The Characterisation of Oilfield Chemicals by Electrospray Ionization ... · The Characterisation of Oilfield Chemicals by Electrospray Ionization Multi-Stage Mass Spectrometry (ESI-MS")

The Characterisation of Oilfield Chemicals by Electrospray

Ionization Multi-Stage Mass Spectrometry (ESI-MS")

by

Paul James M*'Corraack

A thesis submitted to the University of Plymouth

in partial fulfilment for the degree o f

DOCTOR O F PHILOSOPHY

School of Environmental Sciences

Faculty of Science

In collaboration with:

AstraZeneca, Brixham Environmental Laboratory.

April 2003

The Characterisation of Oilfleld Chemicals by Electrospray Ionization Multi-Stage Mass Spectrometry (ESI-MS")

By Paul James Ivf Cormack

ABSTRACT

A diverse range of polar organic chemicals used during the offshore production of crude oils is routinely discharged from oil production platforms in so-called Produced Water (PW). The environmental fate of these chemicals is largely unknown since few methods exist for their detection. In the present study, the use of multistage electrospray ionisation ion trap mass spectrometry (ES1-MS°) was investigated for the detection, identification, characterisation and quantification of compounds in both speciality oilfield chemicals (corrosion inhibitors, scale inhibitors, biocides and demulsifiers) and in Produced Water.

Both positive and negative ion collision induced dissociation (CID) multi-stage mass spectrometry (MS°) was shown to allow high specificity detection and characterisation of alkylbenzenesulfonates, di-[alkyldimethylammonium-ethyl]ethers, alkylbenzyl-dimethylammonium and imidazoline compounds. CID MS° fi-agmentation pathways were determined for di-[alkyldimethylammonium-ethyl]ethers (up to MS*) and imidazoline compounds (up to MS'). CID MS" fragmentation pathways (up to MS"*) were determined for alkylbenzenesulfonaies and alkylbenzyl-dimethylammonium cations and the MS^ produa ions (m/z 119 and m/z 58 respectively) were identified.

Imidazolines, which are widely used in speciality oilfield corrosion inhibitor products and which were shown to be amenable to ESI-MS detection and MS° characterisation, were investigated fiiaher by high performance liquid chromatography (HPLC) coupled with ESI-MS. A HPLC analytical separation method with ESI-MS deteaion was devised for synthetic palmitic and oleic acid-derived 2:1-imidazolines (2:l-PiyOI), 1:1-imidazolines (1:1-PI/0I), monoamide and diamide compounds. The HPLC/ESI-MS responses of 2:1-P1 and 2:1-01 were investigated and detection limits of O.Olug mL'' 2:1-PI and 2:1-01 (signal /noise > 3) were determined in the full scan range m/z 100 - 1000.

A solid phase extraction (SPE) method for the separation of synthetic 2:1-PI and 2:1-01 compounds from crude oils was developed. When followed by HPLC/ESI-MS detection, this allowed the semi-quantitative but sensitive and specific determination of individual imidazolines at low (<10) parts per million concentrations in crude oils. Whilst non-optimised at present, the method is a significant advance and may prove useftil for monitoring downhole and topside oilfield operations.

Although the synthesis of 2-methyl-2-imidazoline was reported over 100 years ago, the existence of reaction intermediates, l:l-imidazoline products and the reaction pathways for the synthesis of 1:1/2:1-imidazolines by thermal reactions of diethyleneiriamine (DETA) with fatty acids has been subject to debate ever since and is still not fiilly understood. It was shown herein that the thermal synthesis of 2:1-palmitic imidazoline proceeds via two different pathways depending on whether the reaction is carried out in the solid phase or in refluxing xylene solvent. Reaction intermediates and final products (1:1- and 2:l-palmitic imidazolines and mono and diamides) were identified and characterised by HPLC/ESI-MS and by MS°. CID MS° fragmentation pathways were determined for 1:1- and 2:1-palmitic imidazolines and 1,2- and 1,3-palmitic and oleic diamides.

The SPE and HPLC/ESI-MS techniques developed in this study should allow the environmental effects and fates of some of these polar compounds to be studied even more fully and a better understanding of the consequences of offshore discharges to be reached. In addition, it is clear that HPLC/ESI-MS" should also allow yet more detailed studies of the reaction mechanisms of the industrial syntheses of some of the commercial products. This too may have consequences for the environment, since improvements in synthesis may lead to higher product purities.

Parts of this research have been published: McCormack, P., Jones, P., Hetheridge, M.J. and Rowland, S.J. (2001) Water Research 35, 3567-3578; McCormack, P., Jones, P. and Rowland, S.J. (2002) Rapid Communications in Mass Speciromefry 16, 705-712.

I l l

Table of Contents

Page

Abstract i i i

Table of Contents iv

List of Tables X

List of Figures xiii

List of Abbreviations XXV

Acknowledgments xxvii

Authors Declaration xxviii

CHAPTER ONE

Introduction 1

1.1 Introduction 2

1.2 Coupling liquid chromatography to mass spectrometry 3

1.3 Eiectrospray ionization mass spectrometry (ESl-MS) 4

1.3.1 Eiectrospray ionization process 5

1.3.2 Advantages and disadvantages of eiectrospray ionization 7

1.3.3 Quadrupole ion trap mass spectrometer (QIT-MS) 9

1.4 The present study 10

C H A P T E R TWO

Analysis of Oilfield Produced Waters and Production Chemicals by

Eiectrospray Ionization Multi-Stage Ion Trap Mass Spectrometry (ESI-MSn) 13

2.1 Introduction 14

2.2 Experimental 15

2.2.1 Chemicals 15

2.2.2 Eiectrospray ionization mass spectrometry (ESI-MS") 16

2.2.3 Produced waters (PW) 16

2.2.4 Stock solutions of standard compounds 17

2.2.5 Oilfield chemicals (DCs) 17

2.3 Results and discussion 17

2.3.1 Produced waters 17

2.3.2 Oilfield chemicals (OCs) 22

2.3.2.1 Corrosion inhibitor CI-D2 22

2.3.2.2 Corrosion inhibitor C1-C3 and C1-B1 28

iv

2.3.2.2 Corrosion inhibitor C1-A3 32

2.4 Conclusions 35

C H A P T E R T H R E E

Development of a solid phase extraction (SPE) procedure for the separation of

imidazoline and related amide oilfield corrosion inhibitors from crude oils. 36

3.1 Introduction 37

2.2 Experimental 40

2.2.1 General chemicals and equipment 40

2.2.2 Thin layer chromatography (TLC) 40

2.2.2.1 Corrosion inhibitor and oil samples 40

2.3.2.2 Thin layer chromatography procedure 40

3.2.3 Solid-phase extraction of corrosion inhibitor CI-El from North Sea 42

Gullfaks crude oil with analysis by infusion and flow injection ESI-

MS (SPE 1-3)

3.2.3.1 Solid phase extraction procedure for corrosion inhibitor CI- 42

El from crude oil

3.2.3.2 Solid-phase extraction procedure for samples SPE 1-3 42

3.2.3.3 Gas chromatography mass spectrometry (GC/MS) analysis of 43

solid-phase eluate fractions

3.2.3.4 Infusion and flow injection electrospray ionisation mass 43

spectrometry (ESI-MS) analysis of solid-phase eluate

fractions

3.2.4 Solid-phase extraction of 2:l-palmitic imidazoline and 2:l-oleic 44

imidazoline (2:1-PI and 2:1-01) from crude oil with analysis by

HPLC/ESI-MS (SPE 4-9)

3.2.4.1 Stock solutions and Samples 44

3.2.4.2 Solid Phase extraction 45

3.2.4.3 Extraction procedure for samples SPE 4-8 46

3.2.4.4 Extraction procedure samples SPE 9 46

3.2.4.5 High Performance Liquid Chromatography (HPLC) 46

3.2.4.6 Analysis of samples SPE 4-9 using HPLC/ESI-MS 47


3.3.1 Thin layer chromatography (TLC) 48

3.3.2 lnf\ision ESl-MS analysis of Cl-El imidazoline corrosion inhibitor 54

intermediate

3.3.3 Solid-phase extraction (SPE) 58

3.3.3.1 Solid-phase extraction of Cl-El (SPE I ) 58

3.3.3.2 Crude oil and CI-El spiked crude oil solid-phase extraction 62

(SPE 2 and 3)

3.3.3.3 Conclusions fi-om the initial solid phase extractions 64

3.3.3.4 Solid Phase Extraction of palmitic and oleic imidazolines 66

from crude oil and analysis using HPLC/ESI-MS

3.3.4 Authentic compounds 69

3.3.5 HPLC/ESI-MS 70

3.3.6 Solid-phase extraction of crude oil spiked with 2:1-palmitic 70

imidazoline (2:1-PI; SPE 4 and SPE 5)

3.3.6.1 Solid-phase extraction of 2:1-palmitic imidazoline spiked 70

crude oil (5 ^g 2:1-PI g oil"*; SPE 4)

3.3.6.2 Solid-phase extraction of 2:1-palmitic imidazoline spiked 75

crude oil (1 ^g 2:1-PI g oil '*; SPE 5)

3.3.6.3 Solid-phase extraction of crude oil spiked with 2:1-palmitic 78

and2:l-oleic imidazoHnes(1 | ig2:l-PI and 1 | i g 2 : l - 0 I g ';

SPE 6)

3.3.6.4 Solid-phase extraction of hexane spiked with 2:1-palmitic 80

and2:l-oleic imidazohnes (1 ng2 : l -PIandl ^g 2:1-01

mL'' hexane; SPE 7)

3.3.6.5 Comparison of solid-phase extraction methods for crude oil 82

spiked with 2:1-palmitic and 2:1-oleic imidazolines (1 ng

2:1-PI and 10 ng 2:1-01 g oil" ' ; SPE 8 and 9)

3.4 Conclusion 83

C H A P T E R FOUR

Development of a high performance liquid chromatography (HPLC)

separation of alkyl-imidazolines and amides with detection by electrospray

ionisation mass spectrometry (ESI-MS). 84

4.1 Introduction 85

4.2 Experimental 86

4.2.1 Chemicals 86

4.2.2 High performance liquid chromatography (HPLC 86

4.2.3 Electrospray ionisation mass spectrometry (ESI-MS") 87

4.2.4 Fourier transform infrared (FT-ER) and *H nuclear magnetic 87

vi

resonance (NMR) spectroscopy

4.2.5 Imidazoline synthesis procedures 88

4.2.5.1 2:1 Thermal reaction of oleic acid with diethylenetriamine 88

4.2.5.2 HPLC/LJV analysis of 2:l-oleic imidazoline synthesis 89

product (sample 01/1)

4.2.5.3 2:1 Thermal reaction of palmitic acid with diethylenetriamine 89

reflux in xylene

4.2.5.4 1:1 Thermal reaction of oleic acid with diethylenetriamine in 90

xylene

4.2.5.5 2:1 Thermal reaction of oleic acid with diethylenetriamine in 90

xylene

4.2.5.6 Vacuum distillation of 95 hour reaction product 91


4.3.1 Solid-phase synthesis of 2:1-oleic imidazoline 94

4.3.2 Synthesis of 2:1-palmitic imidazoline by Dean and Stark reflux in 96

xylene

4.3.3 Investigation of the HPLC separation, UV and ESl-MS detection of 99

2:1-01

4.3.4 HPLC/ESI-MS analysis of 2:1 -PI synthesised by Dean and Stark 105

reflux

4.3.5 Investigation of the HPLC/ESI-MS limits of detection for 2:1-PI in 108

full scan and selected ion monitoring mode

4.3.6 Investigation of ion-pair and solvent systems for the HPLC/ESI-MS 112

detection 1:1-PI and 2:1-PI

4.3.7 Synthesis of l:l-oleic imidazoline by Dean and Stark reflux in 116

xylene

4.3.8 Synthesis of 2:1-oleic imidazoline by Dean and Stark reflux in 120

xylene and purification by vacuum distillation

4.3.9 Investigation of the HPLC/ESI-MS response for 2:1-01 123

4.3.10 HPLC/ESI-MS analysis of a commercial imidazoline-based 127

corrosion inhibitor

4.4 Conclusion 131

C H A P T E R F I V E

Investigation of the thermal synthesis of palmitic acid with diethylenetriamine

(DETA) 132 vii

5.1 Introduction 133

5.2 Experimental 134

5.2.1 Chemicals 134

5.2.2 High performance liquid chromatography with eiectrospray 134

ionisation mass spectrometry (HPLC/ESI-MS) and electrospray

ionisation multistage mass spectrometry (ESI-MS")

5.2.3 Fourier transform infrared (FT-IR) and IH nuclear magnetic 134

resonance (NMR) spectroscopy

5.2.4 Thermal reaction of palmitic acid with diethylenetriamine in xylene 135

solvent

5.2.5 Thermal reaction of palmitic acid with diethylenetriamine without 135

solvent


5 .3.1 Thermal reaction of palmitic acid with diethylenetriamine in xylene 138

solvent

5.3.2 Solid phase thermal reaction of palmitic acid with diethylenetriamine 144

5.3.3 Infusion electrospray ionisation multistage mass spectrometry (ESI- 153

MS") analysis of the solvent and solid phase synthesis products

5.3.3.1 Infusion electrospray ionisation multistage mass 153

spectrometry (ESI-MSn) analysis of the crude reaction

products of the thermal reaction of palmitic acid with

diethylenetriamine in xylene solvent.


spectrometry (ESI-MS°) analysis of the recrystallised product

of the thermal reaction of palmitic acid with

diethylenetriamine in xylene solvent


spectrometry (ESI-MS°) analysis of the crude and

recrystallised palmitic-diamide products and the

recrystallised 2:1 -PI product of the solid phase thermal

reaction of palmitic acid with diethylenetriamine

5.3.4 Fourier transform infrared (FT-ER) spectroscopy analysis of the 175

solvent and solid phase synthesis products

5.3.5 ' H Nuclear magnetic resonance (NMR) spectroscopy analysis of the 176

solvent and solid phase synthesis products

5.3.6 Reaction intermediates and pathways of solvent and solid phase 177

viii

thermal reaction of palmitic acid with DETA

5.4 Conclusions 182

C H A P T E R SIX

Conclusions and Future Work 183

6.1 Conclusions 184

6.2 Future work 188

R E F E R E N C E S 192

APPENDIX 211

IX

List of Tables

Table 2.1 Isotopic Masses for [M2+ + 35Cl-]+ where R l and R2 are alkyi

moieties derived from coco or palm oils.

Table 3.1 Thin layer chromatography of crude oil and imidazoline inhibitor

(CI-EI); sample application and development solvents

Table 3.2 Standard solutions prepared for spiking crude oil

Table 3.3 Samples prepared for solid-phase extraction

Table 3.4 Elution gradients used for HPLC analysis of sample SPE 4 (solvent

A, methanol: 0.1% trifluoroacetic acid v/v and solvent B, 0.1%

trifluoroacetic acid in water v/v)

Table 3.5 Elution gradient used for HPLC analysis of 5 pL injections of

samples SPE 5-9 (solvent A, methanol: 0.1% trifluoroacetic acid v/v

and solvent B, 0.1% trifluoroacetic acid in water v/v)

Table 3.6 Thin layer chromatography Rf values for resolved crude oil and CI-

El imidazoline inhibitor components (TLC 1). Conditions and

procedure described in experimental section 3.2



procedure described in experimental section 3.2


E l imidazoline inhibitor components (TLC 3). Conditions and

procedure described in Experimental section 3.2


EI imidazoline inhibitor components (TLC 4). Conditions and








Table 3.12 Thin layer chromatography Rf values for resolved crude oil and Cl-


Page

28

41

45

45

47

47

50

50

52

52

52

53

53

58

58

72


Table 3.13 Thin layer chromatography Rf values for resolved crude oil and CI- 54



Table 3.14 Thin layer chromatography Rf values for resolved crude oil and CI- 54



Table 3.15 Calculated mono-isotopic masses for some Cig fatty acid-derived

2:1-imidazolines

Table 3.16 Calculated mono-isotopic masses for some Cig fatty acid derived

t:1-imidazolines

Table 3.17 Peak data determined from HPLC/ESI-MS chromatograms of single

ion monitoring oim/z 562.6 (positive ion) for internal standard

2:1-palmitic imidazoline spiked into crude oil (extraction SPE 4)

Table 3.18 Peak data determined from HPLC/ESI-MS extracted ion 72

chromatograms of m/z 562.6 (positive ion) for internal standard

2:1-palmitic imidazoline spiked into crude oil (extraction SPE 4)


chromatograms of analysis 4 for internal standard 2:1-palmitic

imidazoline spiked into crude oil (extraction SPE 4)


chromatograms of m/z 562.6 (positive ion) for 1 g g"' internal

standard 2:1-PI spiked into crude oil (SPE 5)


chromatograms of m/z 562.6 and 614.7 (positive ion) for 2:1-PI and

2:1 -01 spiked into crude oil (1.12/1.04 ng g~' oil)

Table 3.22 Peak data determined fi-om HPLC/ESI-MS extracted ion 81

chromatograms ofm/z 562.6 and 614.7 for2: l-PI and 2:1-01 spiked

into hexane (1.01/1.04 ng mL"' hexane)


chromatograms of m/z 562.6 and 614.7 for 2:1-PI and 2:1-01

standards before and after filtration (1.01/1.04 ^g mL'')


chromatograms of m/z 562.6 and 614.7 (positive ion) for 2:1-PJ and

2:1-01 spiked into crude oil (1.12/10.4 ng g ')


XI

chromatograms of m/z 562.6 and 614.7 (positive ion) for 2:I-PI and

2:1-01 spiked into crude oil (I . I2 /I0 .4 îg g ' ) and extracted by a

confidential SPE method

Table 4.1 HPLC/ESI-MS retention times for extracted mass chromatograms 106

for protonated ions of: PI {p^z 281.3), l : l -P I (m/z 324.4),

monoamide {m/z 342.4). 2:1-PI {pi/z 562.6), and diamide {pi/z

580.6). Conditions as given in Figure 4.11

Table 4.2 Peak areas for detected peaks given in Table 4.1 106

Table 4.3 Relative percentage peak area ratios of peaks given in Table 4.1 107

Table 4.4 Selected ion and extracted ion chromatogram peak data for a series 109

of 2:1-PI (m/z 562.6) standards; 5^L injections on PRP-1 with

gradient [(time/%A) 0/75-0.5/75-15/95; A) 0.1% TFA in methanol

and B) 0.1% TFA]

Table 4.5 Extracted ion chromatogram peak data for a series of 2:1-PI (m/z 111

562.6) standards; 20^L injections on PRP-1 with gradient

[(time/%A) 0/75-0.5/75-11/95; A) 0.1% TFA in methanol and B)

0.1% TFA]

Table 4.6 Extracted ion chromatogram peak data for a series of 2:1-01 (m/z 124

614.7) standards; 20nL injections on PRP-1 with gradient elution


0.1% TFA]

Table 5.1 Gradient elution profile for HPLC/ESI-MS analysis of imidazoline 134

syntheses. Eluents; A) 0.1% TFA in water and B) 0.1% TFA

methanol

Table 5.1 HPLC/ESI-MS peak retention times (R(), signal to noise ratios (S/N) 138

and peak area data acquired from the extracted mass chromatograms

for protonated ions of: !: I -PI (ni/z 324.4), monoamide (m/z 342.4),

2:1-PI (m/z 562.6), and diamide (m/z 580.6) for the crude and

recrystallised products of xylene solvent synthesis (Figures 5.3 and

5.4)

Table 5.3 HPLC/ESI-MS peak retention times (R.), signal to noise ratios (S/N) 146

and peak area data acquired from the extracted mass chromatograms

for protonated ions of: 1:1-PI (m/z 324.4), monoamide (m/z 342.4),

2:1-PI (m/z 562.6), and diamide (m/z 580.6) for the crude and

recrystallised palmitic-diamide and recrystallised 2: l-PI products of

solid phase synthesis (Figures 5.9, 5.10 and 5.11)

xn

Table 5.4 Fourier transform infrared spectra, characteristic absorption 176

frequencies observed for the solvent and solid phase synthesis

products of thermal reaction of palmitic acid with DETA

List of Figures

Page

Figure 1.1 Simplified diagram of the Finnigan Matt LCQ™ electrospray 7

ionisation source with droplet and gas phase ion production.

Figure 2.1 Negative (A) and Positive (B) ion ESNMS mass spectra of produced 19

water extracts: A) ACN solvent and B) MeOH solvent.

Figure 2.2 Negative ion ESI-MS° spectra of precursor ion tn/z 339 shown in 20

Figure 2.1A for produced water and CID MS" fragmentation

pathway of alkylbenzenesulfonates: A) MS^ spectrum of the

precursor ion m/z 339; B) MS^ spectrum of the m/z \ 83 product ion

and C) CID MS" fragmentation pathway of alkylbenzenesulfonates.

MS^ cleavage of the alkyi chain is at the same position for all

homologues producing identical product ions.

Figure 2.2 Negative ion ESI-MS" spectra of precursor ion m/z 339 shown in 24

Figure 2.1A for produced water and CID MS" fragmentation

pathway of alkylbenzenesulfonates: A) MS^ spectrum of the

precursor ion m/z 339; B) MS^ spectrum of the m/z 183 product ion

and C) CID MS" fragmentation pathway of alkylbenzenesulfonates.

MS^ cleavage of the alkyI chain is at the same position for all

homologues producing identical product ions.

Figure 2.4 Positive ion ESI-MS mass spectra of CI-D2 oilfield corrosion 25

inhibitor (1:1 v/v MeOH:H20): A) Full scan m/z 50 - 2000; B)

ZoomScan™ m/z 249A and C) ZoomScan tfi/z 533.4.

Figure 2.5 Positive ion ES1-MS° mass spectra of precursor ion m/z 533.4 in 26

spectrum Figure 2.4 for C1-D2 oilfield corrosion inhibitor: A) MS^

on precursor ion m/z 533.4; B) MS3 on product ion m/z 483.4; C)

MS** on product ion m/z 270.2 and D) MS^ on product ion m/z

226.2.

X l l l

Figure 2.6 Positive ions CID ESI-MS" fragmentation pathway of precursor ion 27

m/z 533.4 in spectrum Figure 2.4A and MS" spectra Figure 2.5A-D

for CI-D2 oilfield corrosion inhibitor

Figure 2.7 Positive ion ESI mass spectra of oilfield corrosion inhibitors A) CI- 30

C3 and B) CI-B1 (1:1 v/v MeOH:H20).

Figure 2.8 Positive ion ESI-MS" mass spectra of ion m/z 304.4 in spectrum 31

Figure 2.7 and CFD MS" fragmentation pathway for CI-C3 oilfield

corrosion inhibitor A) MS^ on precursor ion m/z 304.4; B) MS' on

product ion m/z 212.3; C) CID fragmentation pathway for

alkylbenzyldimethylammonium ions.

Figure 2.9 Positive ion ESI-MS mass spectrum of C1-A3 oilfield corrosion 33

inhibitor (90:10:0.1 v/v/v MeOH:H20:AcOH).

Figure 2.10 Positive ion ESI-MS" mass spectra of ions m/z 350 and 614 shown in 34

Figure 2.9 and CED MS" firagmentation pathway for CI-A3 oilfield

corrosion inhibitor: A) MS^ on precursor ion m/z 350.7; B) MS^ on

product ion m/z 307.2 in A; C) MS^ on product ion m/z 614.7; D)

MS^ on product ion m/z 307.2 in C and E) proposed CID

fragmentation pathway.

Figure 3.1 The structures and naming of the main reagents and products of the 39

thermal reaction of fatty acids with diethylenetriamine for the

synthesis of imidazolines. The names commonly used in the

literature and surfactant industry is given first and is used throughout

this thesis for brevity; whilst the bracketed name is the most recent

systematic name according to guidelines specified by the

International Union of Pure and Applied Chemistry (TUPAC) and

was generated with ACD/ChemSketch 6 software (Advanced

Chemistry Development, Toronto, Canada).

Figure 3.2 Infusion positive ion ESI-MS mass spectrum of Ippm CI-EI 56

imidazoline corrosion inhibitor in methanol:water (7:3 v/v).

Figure 3.3 Infusion positive ion ESI-MS mass spectrum of Ippm CI-EI 56

imidazoline corrosion inhibitor in methanol:water:formic acid

(8:2:0.1 v/v).

Figure 3.4 Expanded spectrum of m/z 600-670 region of Figure 3.2. 57

Figure 3.5 Expanded spectrum of m/z 290-400 region of Figure 3.3. 57

Figure 3.6 GC/MS total ion chromatogram of the SPE hexane eluate from CI- 59

El corrosion inhibitor

XIV

Figure 3.7 Averaged mass spectrums of the major chromatographic peaks 59

shown in Figure 3.6.

Figure 3.8 GC/MS total ion chromatogram of the diethyl ether SPE eluate from 60

corrosion inhibitor CI-El.

Figure 3 .9 Averaged mass spectrums of the major chromatographic peaks 60

shown in Figure 3.8.

Figure 3.10 Infusion positive ion ESI-MS full scan mass spectrum m/z [50-800] 62

of the propan-2-ol:ammonia eluent fraction (0-3mL) from CI-El

corrosion inhibitor extraction SPE 1.

Figure 3.11 Infusion positive ion full scan mass spectrum m/z [50-2000] of the 62

propan-2-ol:ammonia SPE eluate (0-5mL) from GuUfaks crude

oil (SPE 2).

Figure 3.12 Infusion positive ion full scan mass spectrum [m/z 50-800] of the 63

propan-2 ol:ammonia eluate (0-6mL) extracted by SPE from

Gullfaks crude oil spiked with 2000 ppm CI-E1 (SPE 3).

Figure 3.13 Flow injection positive ion full scan mass spectrum [/?z/z 50-800] 64

(averaged across peak) of the propan-2-ol:ammonia eluate (0-6mL)

extracted by SPE fi-om a 2000 ppm CI-E1 spiked crude oil (SPE 3).

Insert shows the total ion chromatogram of the 20 jiL sample

injection into a 150 ^ L min-1 90:10 propan-2-ol:water eluent.

Figure 3.14 HPLC/ESI-MS Total ion chromatogram of CI-El corrosion 67

inhibitor. HyPurity Advance column, 200 ng CI-E1 on column and

isocratic elution with methanol:water:formic 70:30:0.1 v/v/v (See

text for details of peaks 1-5).

Figure 3.15 Extracted ion mass chromatograms of the main 1:1 -imidazoline {m/z 68

348.5) and monoamide (m/z 366.5) observed in CI-El and the mass

si3ectrum of peak 1 shown in Figure 3.14.

Figure 3.16 Positive ESI-MS mass spectra of peaks 2-5 shown in Figure 3.14. 68

Figure 3.17 Extracted ion mass chromatograms (from TIC Figure 3.14) of the 69

main 2:1-imidazolines observed in CI-El: Top to bottom m/z

608.7. 610.7,612.7 and 614.7.

Figure 3.18 HPLC/ESI-MS chromatograms of internal standard 2:1- 73

palmitic imidazoline (5 îg g oil-1) spiked crude oil extraction

SPE 4. a. Total ion chromatogram {m/z 100-1000), b.

extracted ion chromatogram of internal standard {m/z 562.6),

XV

c-f Main Cjg 2:1-imidazoline corrosion inhibitor

components (Wz 614.7,612.7.610.7 and 608.7.

respectively).

Figure 3.19 Mass spectra at the peak retention time, for peaks b, c and d/e shown 74

in Figure 3.18.

Figure 3.20 HPLC/ESI-MS extracted ion chromatograms of crude oil extraction 75

SPE 4. Top to bottom, m/z 614.0, 612.0 and 610.0.

Figure 3.21 HPLC/ESI-MS chromatograms of internal standard 2:1-PI (lîg g *) 77

spiked crude oil extraction SPE 5. a. Total ion chromatogram (m/z

100-1000). b. Extracted ion chromatogram of 2:1-palmitic

imidazoline internal standard (ni/z 562.6), c-f Main Cjg 2:1-

imidazoline corrosion inhibitor components (m/z 614.7,612.7, 610.7

and 608.7, respectively).

Figure 3.22 HPLC/ESI-MS chromatograms of solvent blank injection for crude 78

oil extraction SPE 5. a. Total ion chromatogram {m/z 100-1000), b.

Extracted ion chromatogram of 2:1-palmitic imidazoline internal

standard {m/z 562.6), c-f Main Cig 2:l-imidazoline corrosion

inhibitor components {m/z 614.7,612.7,610.7 and 608.7,

respectively).

Figure 4.1 Proposed reaction pathways for the thermal condensation reaction of 93

fatty acids with diethylenetriamine. Naming as Figure 3.1.

Figure 4.2 Positive ion ESI mass spectrum of 2:l-oleic imidazoline synthesis 95

product sample OI / l . Inftjsion at 3 \yL min*'. Full scan tn/z [50-

2000].

Figure 4.3 Flow injection positive ion ESI mass spectrum of 2:1- oleic 96

imidazoline synthesis product sample 01/2. 5 (iL Injection via "T"

connection into 150 ^ L min-l 0.1% TFA in MeOH, full scan m/z

[100-1000].

Figure 4,4 Apparatus and setup used for xylene reflux synthesis of imidazolines 97

using a Dean andStark trap.

Figure 4.5 Flow injection positive ion ESI mass spectrum of 2:1-palmitic 98

imidazoline synthesis product sample PI/l-7hr. 5 | iL Injection via

"T" connection into 150 ^ L min ' 0.1% TFA in MeOH, full scan m/z

[100-1000].

Figure 4.6 Flow injection positive ion ESI mass spectrum of 2:1-palmitic 98

imidazoline synthesis product sample PI/l-47hr. 5 | iL Injection via

xvi

" T ' connection into 150 ^ L min-I 0.1% TFA in MeOH, f \ i l l scan

m/j [100-1000].

Figure 4.7 HPLC/ESI-MS mass chromatograras of 2:1-oleic imidazoline 101

product by isocratic elution with 0.1% TFA in methanol on PRP-1

colunm: (A) Total ion current of positive ion full scan m/z [100-

1000]; (B) EIC for 2-oleic imidazoline m/z 307.5 and (C) 2:1-oleic

imidazoline m/z 614.7. 5 fiL injections (50 ^ L sample OI/l in 450

îL methanol :water:TFA (70:30:0.1 v/v/v)).

Figure 4.8 HPLC/ESI-MS mass chromatograms of 2:l-oleic imidazoline 102

product by isocratic elution with 0.1% TFA in methanokwater

(90:10 v/v) on PRP-1 column: (A) Total ion current of positive ion

full scan m/z [100-1000]; (B) EIC for 2-oleic imidazoline m/z

307.5 and (C) 2:l-oleic imidazoline m/z 614.7. 5 ^ L injections (50

^ L sample OI/I in 450 ^ L methanol:water:TFA (70:30:0.1 v/v/v)).

Figure 4.9 HPLC/ESI-MS mass chromatograms of 2:1-oleic imidazoline 103

product by gradient elution [(time/%A) 0/70-1/70-15/100; A) 0.1%

TFA in methanol and B) 0.1% TFA] on PRP-1 column: (A) Total

ion current of positive ion frill scan m/z [100-1000]; (B) EIC for

2:l-oleic imidazoline m/z 614.7, (C) 1:1-oleic imidazoline and (D)

2-oleic imidazoline m/z 307.5. 5 iL injections (50 nL sample OI/I

in 450 nL methanol:water:TFA (70:30:0.1 v/v/v)).

Figure 4.10 HPLC/ESI-MS mass chromatograms of 2:1-oleic imidazoline 104

product by gradient elution [(time/%A) 0/80-1/80-15/100; A) 0.1%

TFA in methanol and B) 0.1% TFA] on PRP-1 column: (A) Total

ion current of positive ion ftill scan m/z [100-1000]; (B) EIC for

2:1-oleic imidazoline m/z 614.7, (C) I:l-oleic imidazoline and (D)

2-oleic imidazoline m/z 307.5. 5 | iL injections (50 | iL sample 01/1

in 450 îL methanol:water:TFA (70:30:0.1 v/v/v)).

Figure 4.11 HPLC/ESI-MS mass chromatograms of 2:1-palmitic imidazoline 107

synthesis sub samples by gradient elution [(time/%A) 0/80-1/80-

16/100; A) 0.1% TFA in methanol and B) 0.1% TFA] on PRP-1

column: EIC's for 1:1-PI and 2:I-PI (m/z 325.4 and 562.6) at

7/23/30/47/71 hours and final product.

Figure 4.12 Plot of the percentage relative peak area ratios of 1:1-PI/2:1-PI 108

against reaction time for solvent reflux reaction of palmitic acid with

diethylenetriamine.

xvii

Figure 4.13 Plot of the selected (SIM) and extracted (EIC) ion peak area for 2:1- 110

PI {pi/z 562.6) standards against concentration. Linear trend line and

value shown. Conditions given in Table 4.4.

Figure 4.14 Plot of the extracted (EIC) ion peak area for 2:1 -PI standards {jn/z 111

562.6) against concentration. Order two polynomial trend line,

equation and value shown. Conditions given in Table 4.5.

Figure 4.15 Plot of the selected (SIM) and extracted (EIC) ion peak area for 2:1- 112

PI standards (jn/z 562.6) against concentration. Order two

polynomial trend line, equation and R^ value shown (c/Figure 4.13).

Conditions given in Table 4.4.

Figure 4.16 HPLC/ESI-MS mass chromatograms of 2:l-palmitic imidazoline 113

synthesis 23hr sub sample by gradient elution with

heptafluorobutyric acid ion-pair reagent [(time/%A) 0/80-1/80-

16/100; A) 0.1% HFBA in methanol and B) 0.1% HFBA] on PRP-1

colunm: (A) total ion current chromatogram and (B) EIC's for 1:1-PI

and 2:1-PI (m/z 325.4 and 562.6).

Figure 4.17 HPLC/ESI-MS mass chromatograms of 2:l-palmitic imidazoline 115

synthesis 23hr sub sample by gradient elution with ethanol

[(time/%A) 0/60-0.1/60-15/100; A)0.1%TFA in ethanol and B)

0.1% TFA] on PRP-1 column: (A) total ion current chromatogram

and (B) EIC's for 1:1 -PI and 2:1 -PI {m/z 325.4 and 562.6).

Figure 4.18 HPLC/ESI-MS extracted mass chromatogram of; 1:1 -01 (m/z 350.4; 117

peak 1), monoamide (m/z 368.3; peak 2), 2:1-01 {m/z 614.7; peak 3)

and the diamide (m/z 632.6; peak 4) for l:l-oleic imidazoline

synthesis Ihr sub sample, by gradient elution with ethanol

[(time/%A) 0/55-0.1/55-20/100; A) 0.1% TFA in ethanol and B)

0.1% TFA] on PRP-1 column.

Figure 4.19 Mass spectra of peaks 1 -4 shown in Figure 4.18. 118

Figure 4.20 HPLC/ESI-MS extracted mass chromatograms of 1, 3,19 and 91hr 119

sub samples for l:l-oleic imidazoline synthesis. Peaks 1-4 and

conditions given in Figure 4.18.

Figure 4.21 HPLC/ESI-MS extracted mass chromatograms of 2:1-01 (m/z 350.4; 121

peak 1), monoamide (m/z 368.3; peak 2), 2:1-01 {m/z 614.7; peak 3)

and the diamide {m/z 632.6; peak 4) for 5,23 and 95hr sub samples

of 2:1-oleic imidazoline synthesis. Gradient elution with ethanol

[(time/%A) 0/55-0.1/55-20/100; A) 0.1% TFA in ethanol and B)

xviii

0.1%TFA] on PRP-1 column.

Figure 4.22 HPLC/ESI-N4S extracted mass chromatogram of; 1:1-01 (m/z 350.4; 122

no peak), monoamide {m/z 368.3; no peak), 2:1-01 (m/z 614.7; peak

1) and the diamide {m/z 632.6; peak 2) for oleic diamide. Gradient

elution with methanol [(time/%A) 0/75-0.1/75-17/100; A) 0.1% TEA

in methanol and B) 0.1% TFA] on PRP-1 column.

Figure 4.23 Mass spectra of pâks 1 and 2 Figure 4.22 122

Figure 4.24 Mass spectral ion current response (m/z 614.7) of 2:1-01 standard 125

solutions (0.01 -10 |ig mL'') on consecutive days.

Figure 4.25 Mass spectral ion current response (m/z 614.7) of 2:1-01 standard 125

solutions (0.01 - 1 îg mL'*) on day 1.

Figure 4.26 Mass spectral ion current response {m/z 614.7) of 2:1-01 standard 126

solutions (0.01 - 1 g mL'*) on day 2.

Figure 4.27 Averaged (day 1 and 2) mass spectral ion current response {m/z \ 26

614.7) o f2 : l -OI standard solutions (0.01 - 1 ^gmL"*).

Figure 4.28 HPLC/ESI-MS mass chromatograms of imidazoline corrosion 128

inhibitor product (Cl-El); (A) total ion current chromatogram and

(B) base peak chromatogram. Gradient elution v^th methanol


0,1% TFA] on PRP-1 column.

Figure 4.29 HPLC/ESI-MS extracted mass chromatograms of imidazoline 129

corrosion inhibitor product (CI-El); (A) Ci8:n 1 :l-imidazolines and

(B) Ci8:n/Ci8:n2:l-imidazolines. Conditions as Figure 4.28.


corrosion inhibitor product (CI-El); (A) Cisionionoamides and (B)

Ci8:n/Ci8:ndiamides. Conditions as Figure 4.28.


corrosion inhibitor product (CI-El); (A) C20:n Ll-imidazolines and

(B) C2O:n/C20:n 2:1-imidazolines. Conditions as Figure 4,28.

Figure 5.1 Total ion (TIC; Top) and base peak (BP; Bottom) HPLC/ESI-MS 139

chromatograms of the crude product of the thermal reaction of

palmitic acid with DETA in xylene solvent.


chromatograms of the recrystallised product of the thermal reaction

of palmitic acid with DETA in xylene solvent.

Figure 5.3 HPLC/ESI-MS extracted mass chromatograms from the crude 141

xix

product of the thermal reaction of palmitic acid with DETA in

xylene solvent: (A) I : I -PI {m/z 324.4), (B) palmitic-monoamide (

m/z 342.4), (C) 2:1-PI {m/z 562.6) and (D) palmitic-diamide {m/z

580.6).

Figure 5.4 HPLC/ESI-MS extracted mass chromatograms from the 142

recrystallised product of the thermal reaction of palmitic acid with

DETA in xylene solvent: (A) 1:1 -PI {m/z 324.4), (B) palmitic-

monoamide {m/z 342.4), (C) 2:1-PI {m/z 562.6) and (D) palmitic-

diamide {m/z 580.6).

Figure 5.5 Enlarged HPLC/ESI-MS extracted mass chromatogram of 1,3- and 144

1,2-palmitic-diamide {m/z 580.6) shown in Figure 5.4(D).


chromatograms of the crude palmitic-diamide product of the solid

phase thermal reaction of palmitic acid with DETA.


chromatograms of the recrystallised palmitic-diamide product of the

solid phase thermal reaction of palmitic acid with DETA.


chromatograms of the recrystallised 2:1-PI product of the solid phase

thermal reaction of palmitic acid with DETA.

Figure 5.9 HPLC/ESI-MS extracted mass chromatograms from the crude 150

palmitic-diamide product of the solid phase thermal reaction of

palmitic acid with DETA: (A) 1:1-PI {m/z 324.4), (B) palmitic-


diamide {m/z 580.6).


recrystallised palmitic-diamide product of the solid phase thermal

reaction of palmitic acid with DETA: (A) 1:1-PI {m/z 324.4), (B)

palmitic-monoamide {m/z 342.4), (C) 2:1-PI {m/z 562.6) and (D)

palmitic-diamide {m/z 580.6).


recrystallised 2:1-PI product of the solid phase thermal reaction of

palmitic acid with DETA: (A) 1:I-PI {m/z 324.4), (B) palmitic-


diamide (OT/Z 580.6).

Figure 5.12 Infusion ESI-MS mass spectra of the crude products of the thermal 155

X X

reaction of palmitic acid with DETA in xylene solvent. Positive ion

ftill scan spectra: (A), m/z 50 - 1000 (capillary voltage (+3.88 V), 1''

octapole (-1.39 V), 2"* octapole (-1.39 V) and tube lens (-39.24 V)

and (B), m/z 50 - 700 (capillary voltage (+2.85 V), 1"* octapole (-

1.47 V), 2"* octapole (-6.96 V) and tube lens (-33.22 V). Both

spectra acquired after auto-tuning on ion m/z 324.4 at each m/z

range. The differences illustrate changes in response dependent on

m/z range and tune parameters.

Figure 5.13 ESl-MS ZoomScan mass spectra of the 1:1-PI ion (Left) and 2:1PI 156

ion (Right) shown in the full-scan spectrum (Figure 5.12B).

Figure 5.14 ESl-MS° mass spectra and proposed fragmentation pathways of the 157

l : l -PI precursor ion {m/z 324.4) in the ftill-scan spectrum (Figure

5.128). (A) MS^ of precursor ion m/z 324A (42 % AA), (B) MS^ of

product ion m/z 281.4 (53 % AA) and (C) proposed CID


Figure 5.15 ESI-MS° mass spectra of the 2:1-PI precursor ion (m/z 562.6) in the 158

full-scan spectrum (Figure 5.12B). (A) MS^ of precursor ion m/z

562.6 (42 % AA), (B) MS^ of product ion m/z 281.4 (53 % AA) and

(C) proposed CID fragmentation pathway.

Figure 5.16 Infusion ESl-MS mass spectra of the recrystallised product of the 160

thermal reaction of palmitic acid with DETA in xylene solvent.

Positive ion fii l l scan spectra: (A), auto- tuned on ion m/z 562.6 (m/z

50 - 700, capillary voltage (+30.15 V), 1' octapole (-2.42 V), 2nd

octapole (-5.93 V) and tube lens (-23.12 V) and (B), auto-tuned on

ion m/z 342.4 (m/z 50 - 700, capillary voltage (+30.15 V), 1'

octapole (-1.17 V), 2 "* octapole (-6.88 V) and tube lens (-27.19 V).

Spectra illustrate changes in response dependent on m/z auto-tuned

values.

Figure 5.17 ESl-MS ZoomScan mass spectrum of the palmitic-monoamide ion 161

shown in the full-scan spectrum (Figure 5.16B).

Figure 5.18 ESl-MS" mass spectra of the palmitic-monoamide precursor ion {m/z 161

342.4) in the ftiU-scan spectrum Figure 5.168. (A) MS^ on precursor

ion m/z 342.4 (30 5 AA), (B) MS^ on product ion m/z 324.4 (42 %

AA) and (C) MS' product ion m/z 281.4 (54 % AA).

Figure 5.19 Proposed CID fragmentation pathway of compounds assigned as 1 - 162

and 2-monoamides.

X X I

Figure 5.20 Infusion ESI-MS mass spectra of the crude and recrystallised 166

palmitic-diamide products of the solid phase thermal reaction of

palmitic acid with DETA. Positive ion frill scan spectra: (A), crude

product (auto- tuned on ion m/z 580.6, m/z 50 - 700, capillary

voltage (+42.30 V), 1'* octapole (-2.64 V), 2nd octapole (-6.44 V)

and tube lens (-19.05 V) and (B), recrystallised product, (auto-tuned

on ion m/z 580.6, m/z 50 - 700, capillary voltage (+22.10 V), 1'*

octapole (-2.86 V), 2°^ octapole (-5.93 V) and tube lens (-23.12 V).

Figure 5.21 Infiision ESI-MS mass spectrum of the recrystallised 2:1-PI product 167

of the solid phase thermal reaction of palmitic acid with DETA.

Positive ion frill scan spectra: (auto- tuned on ion m/z 562.6, m/z 50 -

700, capillary voltage (+24.08 V), I"" octapole (-2.93 V), 2nd

octapole (-6.37 V) and tube lens (-27.05 V).

Figure 5.22 ESI-MS ZoomScan mass spectrum of the palmitic-monoamide ion 168

shown in the full-scan spectrum (Figure 5.21).

Figure 5.23 ESI-MS^ CID mass spectrum (A) of the palmitic-diamide precursor 169

ion, m/z 580.6 (40 % AA) in the ftill-scan spectrum (Figure 5.20B).

(B) Shows an enlarged view of ion at m/z 563.6.

Figure 5.24 ESI-MS^ CID mass spectrum of the product ion, m/z 563.5 (35 % 170

AA) in the MS^ spectrum (Figure 5.23).

Figure 5.25 ESI-MS'* CID mass spectrum of the product ion, m/z 282.3 (45 % 170




Figure 5.27 ESI-MS** CID mass spectrum of the product ion, m/z 281.3 (53 % 171






Figure 5.30 Proposed CID fragmentation pathway of compounds assigned as 1,2- 174

and 1,3-diamides.

Figure 5.31 Proposed reaction mechanism for the solid phase thermal reaction of 180

fatty acids with DETA.

Figure 5.32 Proposed reaction mechanism for the solvent based thermal reaction 181

of fatty acids with DETA.

xxii

Figure A . I Fourier transform infrared spectrum of 2:1-palmitic imidazoline 212

synthesised by thermal reaction of palmitic acid with

diethylenetriamine refluxed in xylene solvent (Chapter 4; Section

4.2.5.3): (u/cm *); 1643, 1550 (-NH-C=0), 1608 (C=N).

Figure A.2 Infusion ESI-MS mass spectrum of oleic-diamide product (Chapter 213

4, section 4.3.8). Positive ion full scan spectra: (auto-tuned on ion

m/z 632.6, m/z 50 - 700, capillary voltage (+16.03 V). 1^ octapole (-

3.15 V), 2nd octapole (-6.44 V) and tube lens (-21.17 V). Inset is the

ZoomScan of ion m/z 632.6.

Figure A.3 ESI-MS^ CID mass spectrum of the oleic-diamide precursor ion, m/z 214

632.6 (39 % AA) in the fiill-scan spectrum (Figure A2).

Figure A.4 ESI-MS° mass spectra of the oleic-diamide MS^ product ion {m/z 215

615.6) in the MS^ spectrum Figure A.3. (A) MS^ on precursor ion

m/z 6.15.6 (36 % AA), (B) MS" on product ion m/z 308.3 (43 %

AA).

Figure A.5 ESI-MS^ mass spectrum of the product ion {m/z 325.2; AA 29 %) in 215

the oleic-diamide MS^ spectrum of product ion (m/z 615.6) in the

MS^ spectrum Figure A.3. MS'* on the m/z 308.3 product ion is

identical to Figure A.4B.

Figure A.6 ESI-MS° mass spectra of the oleic-diamide MS^ product ion {m/z 216

614.6) in the MS^ spectrum Figure A.3. (A) MS^ on precursor ion

/n/z6.14.6 (41 % AA), (B) MS'on product ion m/z 307.4 (51 %

AA).

Figure A.7 *H NMR spectrum of the 1,3-oleic diamide product -diamide formed 217

from hydrolysis (during storage) of 2:1-oleic imidazoline (Chapter 4,

section 4.3.8). CDCI3.270 MHz.

Figure A.8 Fourier transform infrared spectrum of the crude 2:1-palmitic 218

imidazoline product of thermal reaction of palmitic acid with DETA

in xylene solvent (Chapter 5; Section 5.2.4): (Wcm*'); 1645, 1550 (-

NH-C=0), 1608 (C=N).

Figure A.9 Fourier transform infrared spectrum of the recrystallised 2:1-palmitic 219

imidazoline product of thermal reaction of palmitic acid with DETA

in xylene solvent (Chapter 5; Section 5.2.4): (u/cm''); 1639, 1552 (-

NH-C=0), 1606 (C=N).

Figure A. 10 Fourier transform infrared spectrum of the crude palmitic-diamide 220

product of solid phase thermal reaction of palmitic acid with DETA

xxiii

(Chapter 5; Section 5.2.5): (u/cm"'); 1639, 1562 (-NH-C=0).

Figure A. 11 Fourier transform infrared spectrum of the recrystallised palmitic- 221

diamide product of solid phase thermal reaction of palmitic acid with

DETA (Chapter 5; Section 5.2.5): (u/cm ' ) ; 1639, 1566 (-NH-CK)).

Figure A. 12 Fourier transform infrared spectrum of the recrystallised 2:1-palmitic 222

imidazoline product of solid phase thermal reaction of palmitic acid

with DETA (Chapter 5; Section 5.2.5): (Wcm"'); 1643, 1550 (-NH-

C=0), 1608 (C=N).

Figure A. 13 ' H N M R spectrum of the 2:1-Palmitic imidazoline product the solid 223

phase synthesis (Section 5.2.5). CDCI3, 270 MHz.

Figure A.14 ' H NMR spectrum of the 1,3-Palmitic diamide product of solid 224

phase synthesis (Section 5.2.5). CDCI3,270 MHz.

X X I V

List of Abbreviations

AA Activation amplitude and Auto-integrated peak area

AC Affinity chromatography

ACN Acetonitrile

AcNA Sodium acetate

AcOH Acetic acid

AH Automatic peak height detection

APCI Atmospheric pressure chemical ionization

API Atmospheric pressure ionization

BDMTDA Benzyldimethyltetradecylammonium

BP Base peak

CE Capillary electrophoresis

CID Collision induced dissociation

CRM Charged residue model

Da Dalton

DBSA Dodecylbenzenesulfonate

DC Direct current

DCM Dichloromethane

DETA Diethylenetri amine

DLI Direct liquid introduction

EIC Extracted ion chromatograph

ESI Electrospray ionisation

EtOH Ethanol

FAB Fast atom bombardment

FT-ICR Fourier transform ion cyclotron resonance

FT-IR Fourier transform infrared spectroscopy

GC Gas chromatography

HFBA Heptafluorobutyric acid

HPLC High performance liquid chromatography

HIC Hydrophobic interaction chromatography

lEM Ion evaporation model

lEC Ion-exchange chromatography

rPA Isopropanol (propan-2-ol)

IPC Ion-pair chromatography

LAS Linear alkylbenzenesulfonates

xxv

LC Liquid chromatography

MeCN Acetonitrile

MeOH Methanol

MS Mass spectrometry

MSDS Material safety data sheet

MS° Multistage mass spectrometry (n = >2

m/z Mass to charge ratio

NH3 Ammonia

NMR Nuclear magnetic resonance spectroscopy

NPLC Normal phase liquid chromatography

OCs Oilfield chemicals

01 Oleic imidazoline

P8 Particle beam

PI Palmitic imidazoline

PW Produced Water

Q Single quadrupole

QqQ Triple quadrupole

Quats Quaternary ammonium compounds

QIT Quadrupole ion trap

RF Radio fiêquency

Rf Retardation factor

RPLC Reverse phase liquid chromatography

R* Retention time

SEC Size exclusion chromatography

SFC Supercritical fluid chromatography

SIM Selected ion monitoring

S/N Signal to noise ratio

SPE Solid-phase extraction

TFA Trifluoroacetic acid

TIC Total ion chromatograph

TOF Time-of-flight

TOFA Tall oil fatty acid

TSP Thermospray

TLC Thin layer chromatography

UV/vis Ultraviolet/visible light range

z s ZoomScan™

xxvi

Acknowledgements

The author wishes to express his sincere thanks to his supervisors. Dr. Phil Jones

(University of Plymouth), Professor Steve J. Rowland (University of Plymouth) and Dr.

Malcolm J. Hetheridge (AstraZeneca Brixham Environmental Laboratory) for their

guidance, help, support and encouragement throughout the project.

The author would like to thank Professor Pavel Nesterenko (Moscow State University) for

advice, helpful discussions and use of novel chromatographic phases. Mr. A. Tonkin

(University of Plymouth) is thanked for invaluable technical assistance and advice with

organic syntheses. The sponsors of the NERC/ industry-funded MIME programme for

access to Produced Waters and oilfield chemicals. A thank you also goes out to an

anonymous industrial sponsor for financial support and provision of chemicals and to the

anonymous referees for helpful suggestions which improved the original manuscripts for

the two published papers.

The author would also like to thank Mr. R. Srodzinski for his assistance with a sometimes

temperamental mass spectrometer and keeping a supply of nitrogen gas available. Mr. A.

Arnold and Sally Madgwick are acknowledged for their invaluable technical assistance and

all other members of the teaching, technical and library staff are thanked for their

assistance.

For making life in Plymouth, in and out of work such an enjoyable experience, a big thank

you to Guy, Julian, Paul (older than me), Emma, Guillaume, Helen, Sarah, James, Andy

and all the other members of PEGG.

Last, but most importantly to my wife, Lesley and son, Carl for putting up with me; thank

you for allowing me to carry out this study.

xxvn

A U T H O R ' S D E C L A R A T I O N

At no time during the registration for the degree of Doctor of Philosophy has the author

been registered for any other University award.

This study was financed with the aid of a studentship from the University of Plymouth and

AstraZeneca, Brixham Environmental Laboratory.

A programme of advanced study was undertaken, with relevant scientific seminars and

conferences attended at which work was oflen presented.

Publications:

Hetheridge M. , McCormack, P,, Jones P. and Nesterenko, P., Analysis of Highly Polar

Low Molecular Weight Organic Molecules: Part 1 - HPLC Separation using Novel

Hypercrosslinked Resin, AstraZeneca Research and Development Bulletin, 100, 2002

(Appended).

Hetheridge M . . McCormack, P., and Rowland S., Analysis of Highly Polar Low

Molecular Weight Organic Molecules: Part 2 -New Methods for the Identification of Polar

Chemicals in Complex Mixtures, AstraZeneca Research and Development Bulletin, 101,

2002 (Appended).

McCormack, P., Jones, P. and Rowland, S.J. (2002), Liquid chromatography/electrospray

ionisation mass spectrometric investigations of imidazoline corrosion inhibitors in crude

oils. Rapid Communications in Mass Spectrometry 16, 705-712 (Appended).

McCormack, P., Jones, P., Hetheridge, M.J. and Rowland, S.J. (2001) Analysis of oilfield

produced waters and production chemicals by electrospray ionisation multi-stage mass

spectrometry (ESI-MS"). Water Research 35, 3567-3578 (Appended).

X X V I I I

Presentation and Conferences Attended:

P. McCormack, P. Jones and S. J. Rowland Analysis Of Oilfield Produced Waters and

Production Chemicals By Electrospray lonisation Multi-Stage Mass Spectrometry (ESI-

MS"). 17*** Montreux Symposium on Liquid Chromatography-Mass Spectrometryy

(LC/MS; SFC/MS; CE/MS; MS/MS), 8-10* November, 2000 (Montreux, Switzerland).

P. McCormack, P. Jones and S. J. Rowland. Analysis of oilfield produced water and

production chemicals by electrospray ionisation multi-stage mass spectrometry (ES-MS").

12* British Organic Geochemical Society Meeting, 5-7 July 2000 (University of Bristol,

UK).

E. Stutt, G. Pan, H. Sturt, P. McCormack, V. Herzl, G. Millward & S. Rowland. Fate of

oil production chemicals in sea water:reactivity of organic constituents in produced waters.

Managing Impacts on the Marine Environment (MIME), final workshop, 12 April 2000

(Heriot-Watt University, Edinburgh, UK).

E. Stutt, G. Pan, H. Sturt, P. McCormack, V. Herzl, G. Millward & S. Rowland. Fate of

oil production chemicals in sea water:reactivity of organic constituents in produced waters.

Progress in Chemical Oceanography I I I , 9 & 10* September 1999, (University of

Plymouth, UK).

Signed

Date.

xxix

"If we knew what it was we were doing, it would not be called

research, would it?"

Albert Einstein

X X X

C H A P T E R ONE

Introduction

1.1 Introduction

The qualitative and quantitative determination of highly polar or ionisable organic

molecules in waters and other matrices is important for a wide range of environmental and

industrial applications. An area of great interest is the investigation of products released

into industrial and domestic effluents. Here, determination of breakdown products and

toxicity and pollution assessments are typically required Generally, target analytes are

present at trace concentrations of Mg L' ' or less, often in the presence of large amounts of

other organic and inorganic compounds. Analytes of interest may have a wide molecular

mass range (<100 to at least 1000 Da) and contain one or more polar or ionisable groups

often including hydroxyl, carboxylic, amino, phosphate/phosphonate, sulfate/sulfonates or

heterocyclic moieties.

High efficiency extraction, preconcentration and chromatographic separation of such

analytes may be difficult due to the hydrophilic nature of the compounds. When examined

by traditional chromatographic methods such as high pressure liquid chromatography

(HPLC), many polar compounds in complex mixtures elute at or close to the void volume,

co-elute with interfering compounds, coelute with homologous analytes or may have

strong surface active properties in reverse phase HPLC systems. This is mainly attributable

to the low capacity and selectivity or restricted pH ranges of most established

chromatographic supports (bonded silicas). Potential methods of separation may also be

limited by the incompatibility with detectors (e.g. liquid chromatography mass

spectrometry (LC/MS) is not compatible with high ionic strength or non-volatile buffers,

ion-pair reagents or solvent modifiers) or the analytes may not be detectable by the most

widely used detectors, such ultraviolet/visible absorption spectrophotometry (UV/vis). A

major problem with most detectors is the lack of specificity for the analysis of moderately

complex samples or the ability to obtain structural information for the identification of

unknown compounds.

The introduction of commercial atmospheric pressure ionization mass spectrometers (API-

MS: electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI))

fi-om at least 1989 onwards* and the coupling of these spectrometers with HPLC systems

{viz: LC/MS) has seen LC/MS evolve into a sensitive, rugged and widely used technique.^"

Of the two most commonly applied API techniques, electrospray ionization (ESI), is

particulariy suitable for highly polar and involatile comj)ounds.^ ESI as the ionization

source for multistage mass spectrometers (MS/MS or MS° n = >2) allows structural

information to be obtained from molecular or pseudomolecular ions. A brief overview of

LC/ESI-MS therefore follows. For illustrative purposes only, particular emphasis is given

to the Finnigan Matt LCQ™ (Thermo Finnigan, San Jose, CA, USA) quadrupole ion trap

mass spectrometer (QIT) which was used for the present study.

1.2 Coupling liquid chromatography to mass spectrometry

The coupling of liquid chromatography to mass spectrometry detectors with various

interfaces has been attempted since at least the late 1960s. For successful coupling of LC

to a mass spectrometer, several problems needed to be overcome. The main problems were

the need for removal of much of the HPLC mobile phase before entry of the eluents into

the mass spectrometer and the requirement for formation of volatilized ions from low

volatility and high polarity analytes. Amongst the first LC/MS interfaces were direct liquid

introduction (DLI), moving belt/wire, thermospray (TSP) and particle beam (PB) devices.

These have been described and reviewed.^ ' More recently, APCI and ESI have proved to

3

be efficient and versatile methods of coupling LC to MS with various interface

designs*' *'*''' and mass analyser types.'''*' '*^ ** The APCl and ESI interfaces differ in the

method of analyte ion formation, eluent flow rate compatibility and polarity of

analyte/eluent optimisation.^

APCI was developed for LC-MS in the early 1970s by Homing and co-workers.*^ *** APCl

is a gas-phase ionisation process initiated by a corona discharge and sustained by the LC

mobile phase vapour which has been rapidly vaporized in a stream of coaxial nitrogen

(along with the analytes) in a high temperature (350 - 500 **C) nebulizer.^'^ APCI is

compatible with high flow rates (> 0.5 mL min i with an optimum at - I m L min"*),

molecular weights generally below 1000 Da with medium to low polarity, reverse and

normal phase solvents. ESI has proven to be a successful interface due to its applicability

to a wide range of compounds, including small highly polar compounds, low-polarity

compounds that can be (de)protonated or which can form cation/anion adduct ions and

high molecular weight biomolecules and polymers from which multiply charged ions may

be produced.

1.3 Electrospray ionization mass spectrometry (ESI-MS)

In 2002, John B. Fenn received a share of the Nobel Prize in Chemistry for his pioneering

work in electrospray ionisation'.

* The prize was awarded jointly to John B. Fenn and Koichi Tanaka '"for their development

of soft desorption ionisation methods for mass spectrometric analyses of biological

macromolecules^^

Electrospray ionization is a process by which gas-phase ions are formed from ions in

solution by applying a high electrical potential to a capillary (containing the solution).

Malcolm Dole and co-workers in the late 1960s and early 1970s were amongst the first to

show that gas-phase ions from polystyrene macromolecules (and later from proteins) could

be produced from an atmospheric electrostatic sprayer interfaced with an ion-drift

spectrometer.'^ The coupling of electrospray ionization to mass spectrometers was

reported in 1984 by Yamishita and Fenn* '*^ and Aleksandrov ei. al}. However, interest in

ESI was greatly increased when Fenn's group in 1988* ' *' showed that proteins may carry

multiple charges (2 to <100) and the distribution of multiply charged ions could be used to

calculate accurate molecular weights. Since that time, LC/ESI-MS has developed rapidly

in applications, interface designs, in MS instrumentation and in computer software for data

analysis. The LC/ESI-MS literature is now extensive, with many reviews, special journal

issues and books having been published recently. *'* ' T h e content of these excellent

works are not repeated here. However, a brief explanation of the ESI process and use with

QIT-MS is appropriate.

1.3.1 Electrospray ionization process

The formation of gas-phase ions from (de)protonated molecules, ammoniated, alkali metal

adducts or anion/cation solution ions can be divided into three stages : v/z; charged

droplet formation; droplet shrinkage and rej)eated disintegrations and finally gas-phase ion

formation.

A high potential is applied to an electrospray capillary ( ± 3 - 5 kV) whilst the sampling

orifice of the mass spectrometer (heated capillary on the LCQ™ instrument) is maintained

at low voltage ( ± 0 - 5 0 V; LCQ™ instrument) to create a potential gradient (Figure 1.1).

Due to the applied electric field, solution ions of the same polarity concentrate at the

capillary tip, which, due to the potential gradient, are drawn out of the capillary tip forming

a 'Taylor cone'. Increasing concentration of ions of similar polarity at the liquid surface,

increases coulombic forces that eventually overcome the surface tension of the liquid-

emitting charged droplets. The charged droplets are drawn down the potential gradient

(and vacuum gradient created by the sampling orifice of the high vacuum in the mass

spectrometer) with solvent evaporation and shrinkage of the droplet increases the

concentration of similar polarity ions at the surface. The coulombic forces again overcome

the surface tension, causing droplet disintegration to smaller droplets which with repeated

droplet disintegrations lead to very small highly charged droplets, which can produce gas-

phase ions. The process is aided at increased flow rates by a coaxial flow of nitrogen

(Figure 1.1) and is also known as "lonspray" and was introduced by Bruins et. al}^ The

process of ionization is very soft and results in mostly pseudomolecular ions with very

little, or no, fragmentation.

However, the actual mechanisms and processes are subject to much debate. There are two

basic theories; the Dole 'charged residue model' (CRM)'^ and the Iribarne and

Thompson 'ion evaporation model' (lEM). '*^®

In the charged residue model, the charged droplets continue to shrink and disintegrate

until a single ion solvated droplet is formed, from which a gas-phase ion is produced on

full evaporation. The ion evaporation model allows for gas-phase ions to be directly

emitted from a very small highly charged droplet surface due to repulsion of charged ions

at the droplet surface, although the eventual fate of the droplets is the same as in the

charged residue model. As previously stated the mechanisms and processes are subject to

much debate. Many reviews and reports detail current thinking in what is an incompletely

understood process with many operating variables. ' ' '* ' ' " '*

Heated stainless steel capillary

Stainless steel electrospray capillary

_+_+.+-+.+.+_+.+.+.+-+.+.+.+ v ? 7 + ^ -.+.+-+-+-+-+_+-+_+-^+_+-+.+ +^ + -+ -_+ +y

I \ + 3 - 5 kV Sample solution

© ® ® ® \ i ffi + +

+ ++ + ++++ + + +

+ +

+ 0 - 50 V

Atmospheric pressure High

vacuum

Figure L I Simplified diagram of the Finnigan Matt LCQ™ electrospray ionisation

source with droplet and gas phase ion production.

1.3.2 Advantages and disadvantages of electrospray ionization

The advantages and disadvantages of ESI interfaces for production of gas-phase ions are

subjective and often somewhat dependent on whether an existing, non-MS based

chromatographic method is being converted to a method based on LC with ESl-MS

detection, or whether a new method is being developed for analytes that were not

previously detectable by other methods. The following are a guide to some of the main

advantages and disadvantages of ESI:

Advantages:

o Suitable for non-volatile, polar and thermally unstable compounds,

o ESI is sensitive (fmol or lower, dependent on analyte).

• Positive and negative ions can be analysed.

• Soft ionization produces mainly molecular or pseudomolecular ions allowing

accurate molecular weights to be determined.

• Optimum chromatographic resolution is not required i f analytes that co-elute have

different m/z and do not cause ESI suppression of one or other analyte.

• Structural information can be determined from molecular or pseudomolecular ions

by collision induced dissociation (CID) and multistage mass spectrometry (MS°).

• Multiply charged ions can be produced, allowing ionised high molecular weight

molecules to be within the mass to charge {m/z) range of most mass analysers.

• Method is compatible with flow rates from nL min'' to 1-2 mL min"'. (Flow rates

over - 3 uL min"' require coaxial N 2 nebulization whilst flow rates above - 50 uL

min ' require auxiliary N 2 nebulization systems (instrument dependent)).

• Method is concentration sensitive. Flow splitting of LC eluents prior to ESI

interface therefore does not reduce sensitivity (excluding peak broadening effects),

thereby allowing conventional chromatography columns (4.6 mm diameter) with 1

- 2 mL min ' flow rates, to be used. The diverted eluent can be directed to other

detectors for complementary data.

• ESI is, or can be made, compatible with many LC techniques such as: reverse phase

(RPLC), normal phase (NPLC), supercritical fluid (SFC), size exclusion (SEC),

ion-exchange (EC), affinity (AC), ion-pair (IPC), hydrophobic interaction (HIC),

capillary electrophoresis (CE) and other electro-chromatography techniques.

Disadvantages:

• ESI is not compatible with high ionic strength solutions or high concentrations

of involatile buffers/mobile phase modifiers used in many traditional

chromatographic methods. ESI normally requires modification of such methods

to allow use of volatile reagents.

8

o Many traditional chromatographic phases and methods require the analyte to be

non-ionised, whereas ESI requires the analyte to be ionised in solution. Post

column addition of acid/base to eluent may be required to adjust solution pH.

o High purity solvents, reagents and chromatographic phases are required in order

to reduce background chemical noise.

• Soft ionization produces mainly molecular or pseudomolecular ions. CID

methods (in source or tandem instruments (MS/MS or MS")) are then required

for obtention of structural information.

1.3.3 Quadrupole ion trap mass spectrometer (QIT-MS)

ESI has been interfaced with most mass analysers (single (Q) and triple (QqQ)

quadrupole, quadrupole ion traps (QIT),^^'^^ time-of-flight (TOP), sector and Fourier

transform ion cyclotron resonance (FT-ICR) instruments '• **' '° ' ' with Q, QqQ and QIT

instruments being the most widespread. The present study was carried out on a Finnigan

Matt LCQ™ QIT instrument for which, a detailed report on the fundamentals, operation,

capabilities and applications is given by Bier and Schwartz." Both Q/QqQ and QIT

instruments use radio frequency (RF) and direct current (DC) voltages for transport,

separation and scanning of ions. QqQ and QIT instruments also allow structural

information to be obtained from collision induced dissociation (CID) of ions in tandem

MS/MS experiments. However, there is a significant difference in the method of

performing operations on the ions between QqQ and QIT instruments.

In triple quadrupole instruments, all ions from the ESI source continuously pass into the

first quadrupole lens (Ql) , and RF and DC voltages are varied to allow ions of a specific

m/z to pass into the next quadrupole (Q2; or straight through to the detector) where a

fiinction on the ions is carried out {i.e. CID experiment). The third quadrupole scans the

resultant or selected ions to the detector. Therefore, each operation on the ion beam is

separated in space {i.e. Q l , Q2 or Q3). In a QIT, the ion beam is allowed to enter the ion

trap (ion injection) for a given amount of time, were the ions are stored (ion isolation), then

allowed to exit (ion ejection) by increasing m/z to the detector. Operations on the ions,

such as CID MS" are carried out on the isolated ions over a period of time, within the same

analyser. It is the inherent ability of the QIT to isolate ions for a period of time that allows

CED MS° experiments where n > 2, and detailed structural information on precursor ions to

be obtained.

1.4 The present study

Large quantities of diverse polar organic chemicals are routinely discharged from oil

production platforms in so-called Produced Water (PW). The detection and environmental

fate of many of these is unknown since few methods exist for their characterisation. At the

inception of the present study it was proposed that ESI-(QIT)MS° had attributes that could

be compatible for the detection and characterisation of a least some of these chemicals.

An investigation was therefore carried out with the following aims:

I . To investigate the use of ESI-MS" and determine its potential for the identification,

characterisation of compounds in speciality oilfield chemicals (corrosion inhibitors, scale

inhibitors, biocides and demulsifiers).

n. Using appropriate model compounds, to investigate and develop compatible L C

methods and chromatographic phases for extraction, separation and quantification of

compounds in speciality oilfield chemicals fiôm environmental matrixes.

10

I I I . To combine the developed extraction, separation and detection techniques for the

qualitative and quantitative analysis of environmental samples.

Chapter 1 has briefly reviewed the development of ESI-MS as a detection method for

HPLC.

Chapter 2 describes preliminary investigations into the use of multi-stage electrospray

ionisation ion trap mass spectrometry (ESI-(QIT)MS° for the identification of compounds

in speciality oilfield chemicals (corrosion inhibitors, scale inhibitors, biocides and

demulsifiers) and oilfield Produced Water. Multiple stage mass spectrometry (MS°) with

both positive and negative ion detection allowed high specificity detection and

characterisation of a wide range of polar and charged molecules. Linear

alkylbenzenesulfonates (LAS), alky I dimethyl benzyl ammonium compounds, [2-(2-alkyl-

4,5-dihydro-1//-imidazol-1 -yl)ethyl]amine (1:1 -Imidazolines), [2-(2-alkyl-4,5-dihydro-1H-

imida2ol-l-yl)ethyl]alkylamide (2:l-lmidazoIines) and a di-[alkyldimethylammonium-

ethyl]ether were all identified and characterised in commercial formulations and/or North

Sea oilfield Produced Water.

Chapter 3 describes the development of solid phase extraction (SPE) procedures for initial

separation of imidazoline/amide oilfield corrosion inhibitors from crude oils prior to

examination by HPLC/ESl-MS.

Chapter 4 describes the development of a high performance liquid chromatography

(HPLC) separation of commercial and synthesised alkyl-imidazolines and amides with

detection by electrospray ionisation mass spectrometry (ESI-MS). Model palmitic and

oleic acid derived 2:1-imidazolines and l:l-imidazolines compounds were synthesised.

I I

The application of the developing HPLC/ESI method was also shown to be a powerful

technique for the investigation of imidazoline synthesis reaction intermediates.

Chapter 5 describes the investigation of the reaction intermediates and pathways of solid

phase and xylene solvent-based thermal reactions of palmitic acid with diethylenetriamine

(DETA). The reaction products were studied by high performance liquid chromatography

(HPLC) separation with electrospray ionisation mass spectrometry (ESI-MS) detection and

structural characterisation was based on electrospray ionisation multistage mass

spectrometry (ESI-MS"), Fourier transform inf i^ red (FT-IR) and *H nuclear magnetic

resonance ( ' H - N M R ) spectroscopy.

Chapter 6 summarises the conclusions from the present study and proposes suggested

further work that may be carried out.

12

CHAPTER TWO

Analysis of Oilfield Produced Water and Production Chemicals by

Electrospray Ionization Multi-Stage Ion Trap Mass Spectrometry (ESI-

MS")

This chapter describes preliminary investigations into the use of electrospray ionisation

multi-stage ion trap mass spectrometry (ESI-MS") for the detection and characterisation of

speciality oilfield chemical components in conmiercial products and in oil platform

Produced Water.

13

2.1 Introduction

When crude oil is produced from offshore oilfields it is associated with varying

proportions of water called Formation Waters.^* In the early stages of oil production, the

water content is usually low, whereas later the proportions can rise to as high as eighty

percent.^' Once the water has been separated from the oil it is known as Produced Water

(PW) and this is discharged into the sea.'*°*'" PW discharges on the UK continental shelf

rose from about 153 million tonnes in 1991 to 244 million tonnes in 2000.'*^

The oil recovery, production and separation processes involve addition of a diverse

mixture of oilfield chemicals (OCs) to the oil-water mixtures. For example, these chemical

mixtures are formulated to act as scale inhibitors to prevent mineral scale deposition

blocking pipework, as corrosion inhibitors to prevent pipe work from attack by the salt

water and dissolved gases, as biocides to prevent bacterial degradation of the oil and other

products, and as emulsion breakers to facilitate oil-water separation.'**' ^^^ Some or all of

these OCs may be discharged to the marine environment along with the PW.'* ' ° In the

North Sea an estimated 5934 tonnes of OCs was discharged in 1989 along with an

estimated 84097 tonnes of drilling chemicals'*^ whilst in 2003 an estimated 13,790 tonnes

of OCs were used and 106,592 tonnes discharged.^'

Although the syntheses of the individual components of the formulated oilfield chemicals

rely substantially on well-known chemical reactions, the products from individual

companies may differ due to blending in order to achieve different activities and ftmctions.

Many of the organic chemicals in the OCs are polar, hydrophilic compounds, which are not

amenable to routine analysis.'* ' ' Establishment of such methods is, therefore, important

to the OC manufacturers, to the oilfield operators and to scientists concerned v^th the fate

and effects, i f any, of PW and OCs in the marine environment.^^'^^'"'^

14

Previously, fast atom bombardment-mass spectrometry (FAB-MS) has been used to good

effect to partially characterise OCs in PW^^ and other spectroscopic methods have been

used in attempts to characterise oilfield chemicals such as imidazoline corrosion

inhibitors.^ Recently, electrospray ionisation mass spectrometry (ESI-MS) has also

proved to be a powerful method for the identification of some constituents of OCs.** ' ' ^

The following study was carried out to determine i f active compounds in a selection of

commercial speciality oilfield chemicals, known to be used in North Sea operations could

be detected, identified and characterised in the products and in extracts of North Sea PW

by ESI-MS°

2.2 Experimental

2.2.1 Chemicals

Ultra pure water was obtained from an Elgastat (Elga, High Wycombe, UK) filtration

system. Al l solvents used were of HPLC grade. Methanol (MeOH) and acetonitrile (ACN)

were obtained from BDH (HyPersolv grade, Poole, Dorset, UK), and dichloromethane

(DCM) from Rathbum Chemicals Ltd (Walkerbum, UK.). Sodium

dodecylbenzenesulfonate (DBSA) was purchased from Aldrich (Poole, Dorset, UK.) and

benzyldimethyltetradecylammonium chloride from Fluka (Buchs SG, SW).

PW samples were supplied by various North Sea oilfield operators and speciality OCs by

various manufacturers.

15

2.2.2 Electrospray ionization mass spectrometry (ESI-MS*)

Mass spectrometry analysis was carried out using a Finnigan Mat LCQ™

(ThermoFinnigan San Jose, CA, USA.) bench top mass spectrometer fitted with an

electrospray interface. Data were acquired and processed with Navigator 1.1 software for

the PW and DBSA samples with a full scan range of m/z 50-1850. Al l other samples were

acquired and processed with Xcalibur 1.0 spl software in the normal full scan range (m/z

50-2000) following an instrument hard/software upgrade. Instrument timing and mass

calibration were carried out and checked using the automatic calibration procedure (tuning

and calibration solutions caffeine (Sigma, St. Louis, MO, USA), MRFA (Finnigan Mat,

San Jose, CA, USA) and Ultramark 1621 (Lancaster Synthesis Inc., Widham, NH, USA) in

methanol:water:acetic acid (50:50:1, v/v/v)). Infiision of PW extracts and OC solutions

were carried out using a built in syringe pump with a Hamilton 1725N (250 ^ L ) syringe

(Reno CA, USA.). Analytes were infused at 3 | iL min V Source voltage, (±) 4.5 kV;

capillary voltage (±) 0-50 V (auto tune function on ion of interest); capillary temperature,

200 ''C; nitrogen sheath gas flow rate, 40 (arbitrary units). Positive and negative ion (±)

MS° analysis of selected ions was performed in the ion trap by collision induced

dissociation (CID) with helium damping gas. MS° ion isolation widths, relative activation

amplitudes and activation Qs were optimised to obtain high response and stability of the

base peak fi-agment ion. High-resolution ZoomScan™ (ZS) was recorded for all ions of

interest. Al l spectral data was recorded and averaged over a one-minute acquisition time.

2.2.3 Produced Water (PW)

PW samples were extracted with DCM (-50 mL). One extract (PW60) was blown to

dryness with nitrogen and the residue re-dissolved in 500 ^ l methanol and 250 j i l Ultra

pure water (PW60MW). A DCM extract fi-om a different PW (PW90) was reduced to - 1

mL using a Kudema Danish controlled evaporation and the remaining extract was divided

into two portions ( - 0.5 mL) in pre-weighed vials and blown down to dryness with

16

nitrogen. The dry residues were re-dissolved in methanol (1 mL; PW90M) and acelonitrile

(1 mL; PW90A). A fiirther 900 ^ L ACN was added to 100 îL of PW90A for analysis.

2.2.4 Stock solutions of standard compounds

Dodecylbenzenesulfonic acid (DBSA) sodium salt (50 mg) was prepared by dissolution in

Ultra pure water and made up to 50 mL. Benzyldimethyltetradecylammonium (BDMTDA)

chloride (50 mg) was made up to 50 mL with methanol. Dilutions of the stock were made

using the required solvents.

2.2.5 Oilfield chemicals (OCs)

Stock solutions of commercial products were prepared as follows: Corrosion inhibitor CI-

D2 (50 ^ L ) was diluted to 50 mL with McOH.HiO (1:1, v/v); Corrosion inhibitor CI-A3

(25 mg) was made up to 50 mL with MeOH; Corrosion inhibitor CI-Bl (116 mg) was

made up to 100 mL with MeOH; Corrosion inhibitor CI-C3 (100 | iL) was made up to 10

mL with MeOH; Demulsifier DM-C2 (25 mg) was made up to 50 mL with MeOH.

Dilutions of the stock solutions were made using the required solvents.

2.3 Results and discussion

2.3.1 Produced Water

Discharged PW is a complex mixture of liquid and particulates and comprises inorganic

and organic compounds of natural origin, applied production chemicals (OCs), and

residues of other platform effluents and deck washes. For an initial evaluation of ESI-MS"

as an analytical technique for PW analysis, DCM extracts were used to obtain polar

organic Auctions. After removal of DCM, the extracts were re-dissolved in various 17

solvents (e.g. methanol, acetonitrile or methanol/water) as it is well known that

electrospray ionisation of compounds varies for different solvents. Negative and positive

ion full scan spectra (± m/z 50 - 1850), ZS and CID MS° spectra of significant ions were

acquired in order to provide data that could be used to identify the unknown extracted

compounds.

In general, negative ion spectra of PW extracts were relatively simple with low baseline

noise. Ions at m/z 297, 311, 325 and 339 were the only significant ions in extracts

dissolved in methanol/water and methanol (not shown). The spectrum of an extract

dissolved in acetonitrile (Figure 2.1 A) also contained these ions but in addition a series of

ions differing by m/z 14 in three clusters were apparent at m/z 423, 529 and 635.

Compounds that correspond to ions in the clusters were not identified but CID MS"

analysis of the ions at m/z 297, 311, 325 and 339 (base peak) indicated a common structure

differing only by 14 Da. Thus, CID MS^ of precursor ions m/z 297, 311, 325 and 339

produced neutral Augment losses to give a common product ion m/z 183 in each case {e.g.

Figure 2.2A). CID MS^ of the m/z 183 product ion in each case produced a fragment ion

m/z 119, representing loss of a neutral 64 Da fragment (Figure 2.2B). Further

fragmentation (MS'*) of the m/z \\9 ions produced no detectable ions.

18

339.7

340.9

100 ^

530.0

311.7 543.8

557.9 40 d

635.8 675.7

7A7.6 297.9

823.6 " - ' I I I

1500

628.6

626.5 628.6

621.7 665.7 621.7

709.6 577.7 622.8

I 624.71 630.8

B 60 753.5 619.6

533.7 174.4 230.5

316.8 797.4

913.1 1180.7

1390.3 1687.1

Figure 2.1 Negative (A) and Positive (B) ion ESI-MS mass spectra of Produced Water

extracts: A) ACN solvent and B) MeOH solvent.

19

100

90

80

3 70

I 60

183.1

50 q

•B 40

Iso 20

10

0 119.3

170.3

,„„,..,,„„p,..|..„,„.,,, 100 150

184.1

197.1 239.1 340.2

275.3 ,|,.Jtj--,,fi.i|i« |iai i.<l|A.iJii|l|<.ll||ii<|ii"|lil>J>ili|l

200 250 300 m/z

r-350

400

100

90 ^

g 7 0

119.2

I ^ I 50

I 40

I 3 0

20

10 80.0

B

183.1

p •,npB^m.|.».|.•. .»• M,• ,M. „.,|„. •, ,,,,, ,,,„,, ,.|,•, •-•p, „, •M^M••p• -• »Mp.. ,l ,. ,M•l»

50 100 150 200 250 300 350 400 mft

Precursor ion

o=s=o MS2

Loss of alkyi chain

R = CeH,„C9H,g.C,oH,, and C „ H „

m/z: 297. 311.325 and 339

o=s=o

Loss of (ii) . I

Product ion

m/z 183

Frsgnncnt ton

m/z119

Figure 2.2 Negative ion ESI-MS° spectra of precursor ion m/z 339 shown in Figure

2.1A for Produced Water and CID MS" fragmentation pathway of alkylbenzenesulfonates:

A) MS^ spectrum of the precursor ion m/z 339; B) MS^ spectrum of the m/z 183 product

ion and C) CID MS° fragmentation pathway of alkylbenzenesulfonates. MS^ cleavage of

the alkyl chain is at the same position for all homologues producing identical product ions.

20

The precursor ions m/z 297, 311 325, 339 and the CCD MS^ product ion m/z 183 are

consistent with those expected of linear alkylbenzenesulfonates (LAS) (Figure 2.2C, (i))^^'

The MS^ product ion m/z ]\9 produced from CID of the m/z 183 product ion via a

neutral loss of 64 Da is consistent with loss of sulfur dioxide (SO2) from an

ethylenebenzenesulfonate ion (Figure 2.2C, (ii)) to yield a ethylenephenoxy ion (Figure

2.2c, (iii)). The fragmentation pathway shown in Figure 2.2C could be deduced for the

MS^ CED of LAS. To the author's knowledge the MS^ m/z 119 ion produced by loss of

SO2 from the CID of the MS^ m/z 183 product ion has not been attributed previously. In

order to confimi that the peaks were due to alkylbenzenesulfonates. a commercial sample

of sodium dodecylbenzenesulfonate was also examined. The negative ion full scan

spectrum (not shown) contained the same four main ions {m/z 297, 311, 325 and 339),

whilst MS° produced identical product ions from each precursor ion to those shown in the

PW components. The negative ion mass spectrum of an oilfield demulsifier DM-C2

(Figure 2.3A) also contained ions at m/z values consistent with the presence of

alkylbenzenesulfonates. MS" analysis shows fragmentations identical to the sodium

dodecylbenzenesulfonate. Thus, ESI-MS° allows unambiguous identification of linear

alkylbenzenesulfonales in both PW and OCs.

The positive ion spectra of the PW extracts were more complex than the negative ion

spectra and the spectrum of the extract dissolved in methanol was very 'noisy'. This is

expected, as the ionisation efficiency of many compounds is greater in methanol/water

mixtures compared with pure methanol. The spectra of extracts dissolved in methanol

(Figure 2.IB) and acetonitrile were very similar with a base peak ion at m/z 628 with a

distribution of ions differing by 2 Da. This is consistent with the presence of two

homologous series of compounds, one containing a further degree of unsaturation. The

spectra are consistent with a diamidoamine synthesised from Tall Oil Fatty Acids (TOFA)

and diethylenetriamine (DETA).^^ Such amides are commonly produced during the

21

manufacture of imidazoline corrosion inhibitors. Also imidazoline compounds readily

hydrolyse to their amide precursor compounds on exposure to air^ and might therefore be

produced in PW from hydrolysis of an imidazoline-based product {yide infra, below

corrosion inhibitor CI-A3). Ions at m/i 489.7, 533.7, 577.7, etc, differing by 44 Da are

tentatively attributed to polyethoxylated compounds, typical of those found in commercial

de-emulsifiers {vide infra).

23.2 Oilfield Chemicals (DCs)

A wide range of OCs are used in offshore oil and gas production. Most are complex

mixtures derived from impure raw materials.^^ Furthermore, many commercial products

are blends of two or more chemical types. For reasons of commercial confidentiality, the

specific chemicals and quantities contained in oilfield products are not generally made

public and only the legally required health and safety data are normally specified on

Material Safety Data Sheets (MSDS). The information given regarding the active

chemicals is generally restricted to the class of compounds (e.g. amines, quaternary

amines, imidazolines, polycarboxylates, phosphonates) and the solvents (aqueous,

methanol or aromatic solvents). Without detailed knowledge of the OC compositions or the

availability of suitable analytical methods, it is difficult for the fate of OCs in operational

processes or in environmental scenarios to be followed. ESI-MS" methods begin to allow

such knowledge to be assembled, particularly i f the mass spectra can be interpreted to

identify unknown constituents, as illustrated in the following experiments in which

samples of commercial OCs were dissolved and diluted in appropriate solvents and

analysed by direct infusion ESI-MS".

2.3.2.1 Corrosion inhibitor CI-D2

CI-D2 is a commercial oilfield corrosion inhibitor stated (MSDS) to contain fatty amine

quaternary salts (10-30%) in water and methanol (10-30%). A positive ESI full scan mass

22

spectrum (Figure 2.4A) of CI-D2 dissolved in methanol:water (1:1, v/v) solvent, showed

three distinctive odd m/z ion series. Ions in the most intense series centred on m/i 249

differed from each other by m/z 14, whilst those in the series around m/z 533 and 1131

differed by m/z 28. These differences beUveen the series were elucidated by the use of the

so-called 'ZoomScan' (ZS) facility on individual ions in each series (ZS allows resolution

of isotope peaks for up to +4 charge-state ions). Thus, pairs of ions in the series at m/z

221.4 - 305.4 (e.g. m/z 249.3 and 249.7) showed mass differences of 0.4 Da (Figure 2.4B).

The m/z 249.4/249.7 ion ratio was consistent with that expected for '^C/ isotopes.

There is no evidence for the presence of chlorine or bromine. The 0.4 m/z differences

suggest the m/z 221.4-305.4 ions are doubly charged ions {m/z = M^V2). By contrast, ZS

analysis of the ion series m/z 477.5-645.5 shows differences of m/z 1.0 between ion

clusters {e.g. m/z 533.4/ 534.4; Figure 2.4C) consistent with singly charged ions {m/z =

M^/1). However, whilst the m/z 533/534 ratio is also consistent with that expected for *^C/

'^C isotopes, the 3:1 ratio of m/z 533 and 535 is also indicative of the presence of a

chlorine atom (viz: ^^CI/"C1). An odd m/z value for the ions indicates that an even number

of nitrogen atoms are present. As fatty amine quaternary salts are expected from the MSDS

description, identification of the compound as a di-quatemary salt is consistent with all the

spectral data (viz: ion series at m/z 221 -305 due to M^""; m/z 533 [M "*" + C\T and m/z 1131

[2M^^+3Cn^ .

In an attempt to identify the chemical more completely, MS" analysis of the ions observed

in the full scan spectrum was carried out. Highly reproducible product ion spectra were

obtained for ions attributed to M " and [M^"^ + Cl"]"^ with up to five CID fragmentation steps

(MS^; Figure 2.5). A fragmentation pathway and a molecular structure for the precursor

ion at m/z 533.5, consistent with the MS" data (Figure 2.5A-D) are shown in Figure 2.6.

The structure is consistent with known synthetic routes to ^>/5-quatemary ammonium

compounds, involving reaction of P-dichloroethylether with alkyl dimethylamine.^ Thus,

23

i f the fatty amine was derived from a coco or palm oil source (cf Cough and Langley^^)

then all the possible ions resulting from combinations of Cg.io.n.N.ie.isalkyl groups can be

identified in the mass spectrum (Table 2.1).

100

90

80

o 70 c ra •a 60 c 1 50 o .a 40 ro <o 30

20

10

0

311.3

297.3

183.1

325.3

339.3

353.2 637.1 687.2 1001.5 1166.2 1445.6 1832.0

500

664.7

1000 m/z

1500 2000

708.7

752.8

620.7 796.7 o 70

576.7 840.8 B 50

a 40 532.7 B84.8

488.7 928.8 444.5 972.9 i i i I " " '

B

1092.7 1344.0 1694.2 1842.7

^w\M|iMiîiiii|iiwr|i,ii| 1500 2000

Figure 2.3 Negative (A) and positive (B) ion ESI-MS mass spectra of DM-C2 oilfield

demulsifier (7:3 v/v MeOHiHjO).

24

100

go

70 q

249.4

| 6 0

| 4 0

^ 30

20

10

0

214.3

165.2

263,4

277.4

291.4

533J

4835

1329.3

477.5

561.4

589.5

617.5

64S.6

6735

600

1131.7

1075.7 , , ^ 127J5

1483.1 1729.6 1973.5

1 • ' t i 200

400 1 — r 800 1000

mlz 1200 1400 1600

•i'"T'"i*"t""r 1800 2000

B

tut mt BO.i

zsoa aij Bij

n 70 to a

» 20 10 0

Figure 2.4 Positive ion ESl-MS mass spectra of C1-D2 oilfield corrosion inhibitor (1:1

v/v MeOHiHjO); A) Full scan m/z 50 - 2000; B) ZoomScan m/z 249.4 and

C) ZoomScan m/z 533.4.

25

B

I2S8.4

400

D

150 200 mtz

Figure 2.5 Positive ion ESI-MS" mass spectra of precursor ion m/z 533.4 in spectrum

Figure 2.4 for CI-D2 oilfield corrosion inhibitor: A) MS^ on precursor ion

m/z 533.4; B) MS^ on product ion m/z 483.4; C) MS** on product ion m/z

270.2 and D) MS^ on product ion m/z 226.2.

26

Precursor ion miz 533.4 Fragment ion mfz 329.3

35, CI

-N-C-C-O-C-CIN c

b

Product ion mfz 270.2 e

H ^

[CH3 H +

^ N ^ ^ C ^ Q H ^ t MW:213

Product ion mfz 226.2

N-C=C

^10^21

g

0=C-CH3 MW; 44.0

Fragment ion m/z 72.1

HaC-N-C^CH, + H,.C„-C=CH 19-9 H

MS3

' a - C ^ H j j j MW:204

Fragment ion m/z 320.2

H^.C^Q-^^—N-C-C-O-C-C-CI

"21^10

Product ion m/z 483.5

N-C-C-O-C-C

35, ' C I -CH3 MW: 50

Fragment ion m/i 102.1

H H - N - C - C - 0 - C = C H ,

CH. H

MW: 154

^^2iCtd"S=CH2 MW168 n

Fragment Ion m/z 58.1

•N-C K

H-N-C=C + H, ,C,o-C=CH,

MW: 168

Figure 2.6 Positive ions CID ESI-MS° fragmentation pathway of precursor ion m/z

533.4 in spectrum Figure 2.4A and MS" spectra Figure 2.5A-D for CI-D2

oilfield corrosion inhibitor.

27

Table 2.1 Isotopic Masses for \M^^ + ^^Cl"]* where Rl and R2 are alkyl moieties

derived from coco or palm oils.

H3 H3 9 9

R 1 - N - C - C - 0 - C - C - N - R 2

H3 H3

R1/R2 Cs Cio C,2 Ci4 C16 C.8

Cs 421.4 449.4 477.5 505.5 533.5 561.5

Cio 449.4 477.5 505.5 533.5 561.5 589.6

C12 477.5 505.5 533.5 561.5 589.6 617.6

C|4 505.5 533.5 561.5 589.6 617.6 645.6

C16 533.5 561.5 589.6 617.6 645.6 673.7

C18 561.5 589.6 617.6 645.6 673.7 701.7

2.3.2.2 Conroslon Inhibitors CI-C3 and CI-B1

CI-C3 and CI-Bl are commercial oilfield corrosion inhibitors stated (MSDS) to comprise:

ethoxylated amines and quaternary compounds (5-10%), butyl glycol (20-30%) and

monoethylene glycol (20-30%) in water (CI-C3) and benzyl chloride quat amine (5-10%)

and methanol (1-5%) (CI-Bl). Positive ion ESI-MS spectra suggest that both formulations

contain quaternary amines corresponding to alkylbenzyldimethylammonium

(benzalkonium) compounds (Figures 2.7A and B). The spectra show that the alkyl chain

source is different for each product, with CI-C3 having a C12 (base peak), C14, Cie and Cig

distribution whilst CI-Bl has only two ions for C16 and C18 (base peak). This has been

shown previously by ESI-MS by Gough and Langley." The more powerful multi-stage

MS" analysis of the benzalkonium ions produced highly reproducible fragmentations with

28

masses differing only by the alkyi chain lengths. Thus, CID MS^ of the benzalkonium

precursor ion produced nvo ions (Figure 2.8A) with the base peak m/z corresponding to a

neutral loss of 92.0 Da, consistent with fragmentation of the benzyl moiety with a proton

migration to effect loss of a methylbenzene and yield an iminium ion (Figure 2.8C). The

product ion at m/z 91.0 is consistent with a benzyl cation (tropylium ion) commonly seen

in electron ionisation-MS of aromatic compounds, and a neutral loss of

alkyldimethylamine (Figure 2.8C). Both of the MS^ fragment ions result from cleavage of

the same nitrogen-benzyl bond. CID MS^ of the MS^ iminium ion (Figure 2.8B) results in

loss of an alkene molecule via a 1,5 proton shift M^'Lafferty rearrangement^^ to yield a m/z

58 iminium ion (Figure 2.8C). MS° analysis of authentic

benzyldimethyltetradecylammonium chloride (BDMTDACI) produced identical

fragmentation spectra to that for the benzalkonium ions in the corrosion inhibitors.

Following the publication of these results^ a report by Ferrer and Furlong^^ showed

similar results for CID MS^ fragmentation of Cu and C M dimethylbenzylammonium ions

although MS^ fragmentations were not carried out. The reproducibility of the CID MS°

spectra allows unambiguous identification of the benzalkonium ions.

Corrosion inhibitor CI-C3 also contained ethoxylated amines (MSDS). Ions due to these

are also seen in the positive ESI-MS spectrum (Figure 2.7A) as at least three series of ions

differing by 44 Da (v/z: corresponding to -C2H4O-) between m/z 500 - 1300. Although the

MSDS for corrosion inhibitor CI-Bl does not state that it contains ethoxylated compounds

there are clearly several series of ions differing by 44 Da in the spectrum and some have

similar m/z values to those seen in CI-C3 and in the demulsifier DM-C2 (Figure 2.3B). The

even m/z ions infer an odd number of nitrogen atoms in the compounds and the presence of

several series suggests that both CI-Bl and DM-C2 also contain ethoxylated amines. Series

differing by m/z 44 are also observed in positive ion ESI-MS spectra of the Produced

Water (e.g. Figure 2.IB), suggesting these demulsifiers may be discharged into the

29

environment. However in the PW the ethoxylated compounds differed by 1 Da (reliably

measured by ZS) from those in DM-C2 and CI-C3.

304.5 100 -

5 50 -332.5

872.8 9 6 ° - ^ 1048.8 8 2 8 . a _

809.8 360.5

1092.7 388.6 1136.8

639.8 1180.8 1523.2 1917.1

2000

100

90

80

S 70

S 60 c I 50

0)

388.6

360.7

-30 -E

20 ^

- 296.6 10 i 234.5 1

0

B

664.7 620.7 765.6

5 0 J ^ 897.5

1000 m/z

1202.9 1291.7 1684.5 1959.8 ' • " l ' ^ " T ^ - - T " ' i - - ' ' i " M | I

1500 2000

Figure 2.7 Positive ion ESI mass spectra of oilfield corrosion inhibitors A) CI-C3 and

B)CI-B1 (1:1 v/v MeOHiHjO).

30

iGO n 00

ao • 70

I eo I so

I *° I 30

20 to 0

100

SO

80

S ^

i ^ I 50

I '° I 30

20 10

100 ISO 300 250 300 "350" 200 300

B

Precursor ion

m/z 304.4 R = CgH g

>•- * Fragment ion

m/z 58.0

R

MW: 154.2

MS2

a -

\ MS3

- C —

c. II W

Fragment ion nr>/z91.0

//

Product ion m/z 212.3

\ N

MW: 213.3

MW: 92.0

Figure 2.8 Positive ion ESI-MS° mass spectra of ion m/z 304.4 in spectrum Figure 2.7

and CID MS" fi^gmentation pathway for C1-C3 oilfield corrosion inhibitor:

A) MS^ on precursor ion m/z 304.4; B) MS' on product ion m/z 212.3; C)

CID fragmentation pathway for alkylbenzyldimethylammonium ions.

31

2.3.2.3 Corrosion Inhibitor CI-A3

Corrosion inhibitor C1-A3 is a commercial oilfield corrosion inhibitor with stated

composition (MSDS) comprising 10-15% solvent naphtha (petroleum), 1-5%

butoxyethanol and 20-40% long chain alkyl imidazoline. A positive ion ESI ftill scan

spectrum (Figure 2.9) of a solution of CI-A3 contained two prominent sets of ions at m/z

350 and 612. These are near identical to those reported by Gough and Langley^^ for

TOFA/DETA-derived imidazolines. Gough and Langley attribute the spectra to protonated

l:l-imidazolines ([2-(2-alkyl-4.5-dihydro-l//-imidazol-l-yl)ethylamine]) and 2:1-

imidazolines (2-(2-alkyl-4,5-dihydro-l//-imidazol-l-yl)ethyl]alkylamide) (Figure 2.9). The

peak distributions differ by 2 Da in each group, which is consistent with a natural

distribution of unsaturated acids expected from reactants derived from a natural source

such as a Tall Oil. MS^ analysis of the precursor ions m/z 350.7 and 614.7 (Figure 2.10A

and C), corresponding to imidazolines with alkyl moieties R i=Ci6H3i and R2=Ci7H33,

shows the formation of a protonated 2-alkylimidazoline moiety (Figure 2.10E) as the base

peak ion for both ions via losses of etheneamine and N-ethene-alkylamide respectively.

MS^ fragmentation of the product ion m/z 307 (Figure 2.10B and D) produced identical

spectra consistent with the loss of the alkyl chain to give a protonated 2-etheneimidazoline

(Figure 2.10E). Further fragmentation produced no ions above the m/z 50 lower mass limit

of the instrument. Spectra were obtained for other ions in the two groups producing

product ions that varied by 2 Da, confirming the differences were due to the degree of

unsaturation of the alkyl chains. A fragmentation pathway that is consistent with the

structures of the imidazoline compounds is given in Figure 2.10E.

32

348.6 612.6

614.6 (2)

350.6

610.7

305.6 351.6

630.5 393.4 219.3

636.6 600.8 960.1

r •NH-

1:1-lmidazolines

([2-(2-alkyl-4.5-dihydro-1H-imida20l-1-yOelhyIlam!ne)

1 •NH

2:1-lmidazolines

([2-{2-alkyl-4.5-dihydro-1H-imidazol-1-yOethy!]alkylamide)

1286.5 1391.5 1602.6

" • " • ' t " " t " 1500

Figure 2.9 Positive ion ESl-MS mass spectrum of CI-A3 oilfield corrosion inhibitor

(90:10:0.1 v/v/vMeOH:H20:AcOH).

33

B

D

400 SOO 600 TOO 600

(1) H N y i l i ] ^

R1

m/z 350.7 R1 = C^^^^

R1

m/z 614.7 R1 ^CigHa,

Loss of

Loss of

(3)

HN^NH

J/ R1

m/z 307.2

Loss of /UkyI group

(4)

HN^^NH

mfz 97.0

E

Figure 2.10 Positive ion ESI-MS° mass spectra of ions m/z 350 and 614 shown in Figure

2.9 and CID MS" fragmentation pathway for CI-A3 oilfield corrosion inhibitor; A) MS2 on

precursor ion m/z 350.7; B) MS3 on product ion m/z 307.2 in A; C) MS2 on product ion

m/z 614.7; D) MS^ on product ion m/z 307.2 in C and E) proposed CID fragmentation

pathway.

34

2.4 Conclusions

Examination of a range of oilfield chemicals (OCs) and of oilfield platform Produced

Water (PW) by electrospray ionization ion trap multi-stage mass spectrometry has

demonstrated for the first time that the technique is very powerful for the identification and

characterisation of polar chemicals used as demulsifiers, corrosion inhibitors and biocides,

for example.

A range of imidazolines, alkylbenzene sulfonates, quaternary ammonium compounds

(quats) and ethoxylates have all been identified, some for the first time in OCs and PW.

The particular advantages of the ion trap multi-stage MS method are: the possibility of

both positive and negative ion detection {e.g. for quats and sulfonates respectively); the

ability through the so-called 'ZoomScan™' facility to determine the accurate mass

differences between ion pairs, thus allowing differentiation of the multiple charge state of

the ions; the collision induced dissociation multistage mass spectrometry allowing

ft-agmentation pathways to be studied in up to five steps, thereby allowing previously

unknown compounds to be identified.

35

CHAPTER T H R E E

Development of a solid phase extraction (SPE) procedure for the

separation of imidazoline and related amide oilfield corrosion inhibitors

from crude oils

This chapter describes the development of solid phase extraction (SPE) procedures for

initial separation of imidazoline/amide oilfield corrosion inhibitors from crude oils prior to

examination by HPLC/ESl-MS.

36

3.1 Introduction

The advent of electrospray ionisation-mass spectrometry (ESI-MS) has seen application of

the technique to the identification of a growing number of polar chemicals in

environmental and industrial matrices. '*' ' '*'"'™"^^ In Chapter 2, infusion ESI-MS was

shown to be applicable to characterisation and determination of oil field chemicals as

diverse as positively charged quaternary benzalkonium chlorides ('Quats') and aruons of

linear alkylbenzene sulfonates CLAS') .^ Gough and Langley^^ also demonstrated

application of LC/ESI-MS techniques to the detection of a variety of polar organics in

oilfield chemical formulations and oilfield Produced Water (PW) including Quats (used as

biocides) and corrosion inhibitors such as the so-called 'imidazolines' ([2-(2-alkyl-4,5-

dihydro-l//-imidazol-l-yl)ethyl]amine (1:1-Imidazolines). [2-(2-alkyl-4,5-dihydro-l//-

imidazol-l-yl)ethyl]alkylamide (2:1-Imidazolines); structures VI I and VII I respectively;

Figure 3.1) produced by thermal reaction of fatty acids with diethylenetriamine^^ "'^^

(Figure 3.1 shows the structures and naming of the main reagents, intermediates and

products of the reaction). However, although detection of oilfield chemicals has been

reported, few authors have reported ESI-MS methods for the quantitation of polars such as

imidazolines'*^'"; and there are no reports of their determination in complex industrial

matrices such as crude oil. For imidazolines this is important for the assessment of the

efficiency of both downhole inhibitor addition (so-called "squeezing")'^ and to topside

operations where control of dosing rates for the protection of metalwork reduces over

dosing and consequent economic and environmental costs. Whilst methods such as thin-

layer chromatography (TLC) have been used previously to detect imidazolines in crude

oils,'^ such methods at best only allow total imidazolines to be determined. Solid-phase

extraction (SPE) methods have been reported"* '" for extraction of imidazolines fi-om PW"

and brines,'*^ but there appear to be no reports of the separation of imidazolines from crude

oils using SPE.

37

A system is required which allows crude oil (principally hydrocarbon) components to be

eluted through a SPE column whilst retaining the imidazoline/amide compounds, followed

by elution of the latter in a minimum of solvent whilst asphaltenes and other polar oil

compounds are retained. Such an elution solvent system would need to be compatible with

ESI-MS.

38

o

(Cartwxylic add) Fatty Acid

H 2 N ^ x \ ^ x - N ^ N H 2 Diethylenetriamine (DETA)

^ (A/-(2-aminoethyl)ethane-1,2-diamine)

3 2 H 1-Monoamide N H ^ O (A/-{2-((2-aminoethyl)aminoJetfiyl}aIkylamide)

3 o 1 2-Monoamide

I V H a N ^ / ^ ^ s ^ N H j (A/,Wîs(2-aminoethyl)alkylamide)

R ^ O

H 2

Ts ^ lY 1.3-Diamide

^ 3 H o (A/-[2-(2-alkylamino-ethylamino)ethyl]alkylamide)

3 2 H VI H j N ^ ^ ^ . ^ ^ N ^ R 1,2-Diamide V 1 "

^ O (A/-^2-amino-ethyI)-A/-{2-alkylamino-ethyl)alkylamide)

VII NON^/^NHS 1:1-lmidazolines

^ ([2-{2-alkyI-4.5-dihydro-1HHmidazol-1-yl)ethyl]amine)

2:1-lmidazoljnes VII I N ^ ^ N H

1 ([2-(2-aIkyl-4.5-dihydro-1H-imidazol-1-yl)ethyl]alkylamide) R

IX H^NH 2-alkylmidazolines

^ (2-alkyl-4,5-dihydro-1H-imidazole)

Figure 3.1 The structures and naming of the main reagents and products of the thermal

reaction of fatty acids with diethylenetriamine for the synthesis of imidazolines. The name

commonly used in the literature and surfactant industry is given first and is used

throughout this thesis for brevity; whilst the bracketed name is the most recent systematic

name according to guidelines specified by the International Union of Pure and Applied

Chemistry (lUPAC) and was generated with ACD/ChemSketch 6 software (Advanced

Chemistry Development, Toronto, Canada).

39

3.2 Experimental

3.2.1 General chemicals and equipment

Ultra pure water was obtained from an Elgastat filtration system (Elga, High Wycombe,

UK). Al l solvents used were HPLC grade except glass distilled diethylether (ether)

(Rathbum Chemicals Ltd, Walkerbum, UK. and BDH, Poole, UK). Methanol (MeOH),

propan-2-ol (IPA), ammonia (0.88) and trifluoroacetic acid (TFA) were HyPersolv grade

obtained from BDH (Poole, UK). Dichloromethane (DCM), ethanol (EtOH) and hexane

were obtained from Rathbum Chemicals Ltd (Walkerbum, UK). Glass vials (7 and 15 mL)

with Teflon lined caps were obtained from Supeico (Poole, UK) whilst auto sampler glass

vials (2 mL) with polypropylene screw caps and silicone/PTFE seals were obtained from

Chromacol (Welwyn Garden City, UK).

3.2.2 Thin layer chromatography (TLC)

3.2.2.1 Corrosion inhibitor and oil samples

A biodegraded North Sea cmde oil (Gullfaks crude, PEP Ltd., Plymouth, UK) and an

imidazoline corrosion inhibitor intermediate product (our code Cl-El) supplied by a

commercial manufacturer, were used. The material safety data sheet (MSDS) for CI-EI

stated that the product comprised: l,2,4-trimethylben2ene (1-5%), solvent naphtha

(petroleum) heavy aromatic (20-30%) and long chain alkyl imidazoline (60-70%).

3.2.2.2 Thin layer chromatography procedure

Thin layer chromatography was carried out using SILGUR-25 (silica gel 60A with

Kieselguhr pre-concentration zone; 250um x 20 x 20 cm glass plates; Machery-Nalgel

GmbH & Co. Diiren, Germany (Plate 1-5, Table 3.1)) and laboratory-prepared plates of

silica gel (60G, 0.5 mm x 20 x 20 cm (Plate 6-9, Table 3.1). Plates were oven-dried (160

40

°C for 90 minutes) before use. Developing tanks lined with blotting paper were allowed to

equilibrate with the solvent for at least 90 minutes before development Sample application

was by 2 (iL micro capillaries (micro-caps, CAMAG, Muttenz, Switzerland) to the silica

phase (to produce a smaller origin spot) except for plate 1 (Table 3.1) where the sample

was applied to the Kieselguhr pre-concentration zone. Samples were diluted in DCM (100

mg oil mL * and 10 mg CI-El mL *) before use and spots ranging from 1-8 j iL were

applied. Afêr sample application, plates were air dried (10-15 minutes) before

development. After a first development in diethyl ether, hexane or DCM, plates were air-

dried (10-15 minutes) before visualisation or a second development stage. After second

stage development in propan-2-ol:ammonia (8:2 v/v) plates were air dried (10-15 minutes

and 40°C for -30 minutes). Visualisation was by UV light source at 254 and 366nm

followed by development in iodine vapour. Retardation factors (Rf) were calculated for

product spots. For large spots or streaks an Rf range was measured for the lower and upper

limits of the product.

Table 3.1 Thin layer chromatography of crude oil and imidazoline inhibitor (CI-El);

sample application and development solvents

TLC Plate

Plate development solvents and sample application of crude oil and imidazoline inhibitor (CI-El) .

1 Sample spots applied to the Kieselguhr pre-concentration zone and developed first in diethyl ether and then in propan-2-ol;ammonia (8:2 v/v).

2 Sample spots applied to the silica and developed first in diethyl ether and then in propan-2-ol:ammonia (8:2 v/v).

3 Sample spots applied to the silica and developed in diethyl ether. 4 Sample spots applied to the silica and developed in hexane. 5 Sample spots applied to the silica and developed in dichloromethane.

6 Sample spots applied to the silica and developed first in diethyl ether and then methanol:ammonia(8:2 v/v).

7 Sample spots applied to the silica and developed first in diethyl ether and then methanol.

8 Sample spots applied to the silica and developed first in diethyl ether and then propan-2-ol.

9 Sample spots applied to the silica and developed first in diethyl ether and then methanol:glacial acetic acid (8:1 v/v).

41

3.2.3 Solid-phase extraction of corrosion inhibitor Ci-EJ from lôrth Sea Guiifaks

crude oil with analysis by infusion and flow injection ESI-MS (SPE1-3)

3.2.3.1 Solid phase extraction procedure for corrosion inhibitor CI-E1 from crude oil

A polyethylene solid-phase extraction reservoir (6 mL; Isolute, International Sorbent

Technology, Hengoed, UK) was packed dry with silica gel (60G, 500 mg) and fitted with a

defatted cotton wool plug. Solid-phase extraction sample SPE 1 (see below) was eluted

under positive pressure using an adapter and Luer-tipped syringe. Samples SPE 2 and 3

were eluted using a vacuum manifold extraction system (Isolute, International Sorbent

Technology, Hengoed, UK) with a flow rate of - ImL min".

Stock solutions (1 g CI-EI in 10 mL hexane) were made up daily as required in glass

volumetric flasks and transferred to glass vials (15 mL). Samples were: SPE 1, 200 ^ L of

stock CI-El solution (20 mg Cl-El); SPE 2, crude oil prepared by diluting 500 mg oil with

5 mL hexane and SPE 3, 2000 ppm (2 mg mL'*). CI-El in crude oil was prepared by

spiking 10 ^ L of stock CI-El into 500 mg oil and dissolving in 5 mL hexane.

3.2.3.2 Solid-phase extraction procedure for samples SPE 1-3

The SPE column was washed and pre-equilibrated with 6 mL hexane before applying the

sample. Sample SPE 1, was transferred onto the column using a glass pipette whilst

samples SPE 2 and 3 were syringed onto the column under gentle vacuum (the column was

not allowed to run dry except upon final elution). The column was eluted with hexane,

diethyl ether and twice with propan-2-ol:ammonia (8:2 v/v) successively and the individual

fractions retained. However, because the approach was developmental, the volumes of

eluents used varied somewhat (SPE 1: hexane 3 mL, diethyl ether 4 mL, propan-2-

ol:ammonia (8:2 v/v) 3 mL and 5 mL; SPE 2: hexane 3 and 5mL, diethyl ether 6 and 2 mL,

propan-2-ol:ammonia (8:2 v/v) 6 and 3 mL and SPE 3: hexane 5 and 3 mL, diethyl ether 5

42

and 2mL, propan-2-ol:ammonia (8:2 v/v) 5 and 2 mL). Glass vials (7 mL) with

aluminium-lined caps were used for ftuction collection. Selected fractions were blown dry

under a nitrogen stream with heating to 60 °C, except firactions from the spiked crude oil

(SPE 3) which were blown down to - 1 and 0.25 mL.

3.2.3.3 Gas chromatography mass spectrometry (GC/MS) analysis of solid-phase eluate

fractions

Gas chromatography mass spectrometry (GC/MS) carried out using a Hewlett Packard

5890 series n GC with a 5970 mass selective detector (MSD). The column was a HP 1

Ultra (12 m X 0.2 mm i d.) programmed fi-om 40-300 °C at 5 °C min ' plus a 10-minute

hold. The injection volume was 0.5 \iL. Analyte fractions prepared for GC-MS analysis

were: SPE 1; 1.8 mg dry residue of 3 mL hexane eluate fraction dissolved in 4 mL

dichloromethane (-0.5 mg mL"') and 2.5 mg dry residue of 4 mL diethyl ether eluate

fi^ction dissolved in 5mL dichloromethane (-^.5 mg mL'').

3.2.3.4 Infusion and flow injection electrospray ionisation mass spectrometry (ESI-MS)

analysis of solid-phase eluate fractions


(ThermoFinnigan, San Jose, CA, USA.) bench top mass spectrometer. The LCQ was used

with an electrospray interface and Xcalibur 1.0 spl software (ThermoFinnigan). Infusion

of extracts (3 ^ L min"') was carried out using the built in syringe pump with a Hamilton

I725N syringe (250 | iL ; Reno CA, USA.). The instrument was auto-tuned on analyte ion

m/z 610.7. Flow injection was performed using a 20 ^ L sample injection into a 150 ^ L

min"' 90:10 propan-2-ol:water eluent.

Analyte fractions prepared for ESI-MS analysis were: SPE 1; 11 mg dry residue of propan-

2-ol:ammonia 3 mL eluate fraction dissolved in propan-2-ol (2 mL). 100 j iL transferred to

2 mL glass vial and 900 j iL propan-2-ol added. SPE 2; 2 mg dry residue of the 6 mL 43

propan-2-ol:ammonia eluate fraction dissolved in propan-2-ol (2mL). 100 | i L transferred

to 2 mL glass vial and 900 | i l propan-2-ol added. SPE 3; 100 ^ L of --1 mL residual propan-

2-ol:anmionia eluate (assuming 100% recovery, then 2000 ppm) transferred to 2 mL glass

vial and 900 ^ L propan-2-ol added (200 ppm).

Infrision ESI-MS analysis of corrosion inhibitor CI-EI (Stock 0.0643g CI-El up to 50mL

methanol; 1287 (ig mL'*, ppm) was carried out at a concentration of - 1 ppm (lOOOx

dilution of stock) in two solvents, Sample X (MeOH:water; 7:3 v/v) and Sample Y

(MeOH:water:formic; 80:20:0.1 v/v/v) in order to characterise the initial product.

3.2.4 Solid-phase extraction of 2:1-palmitic imidazoline and 2:]-oleic imidazoline (2:1-

PI and 2:1- OI)from crude oil with analysis by HPLC/ESi-MS (SPE 4-9)

3.2.4.1 Stock solutions and Samples

A crude oil sample from a Middle Eastern oilfield which had being treated with

imidazoline based corrosion inhibitor was used (supplied by a commercial manufacturer).

The oil was supplied in 1 L aluminium flasks. Stock solutions of 2:1-palmitic imidazoline

(2:I-PI; R and Ri = C i 5 H 3 i , structure V m , Figure 3.1; Chapter 4 for synthesis details) and

2:l-oleic imidazoline (2:1-01; R and Ri = C17H33, structure VII I , Figure 3.1;) were

prepared in glass volumetric flasks and transferred to 15 mL glass vials. Standard solutions

for spiking crude oil samples for SPE were made up as described in Table 3.2.

44

Table 3.2 Standard solutions prepared for spiking crude oil

Standard Analyte/Concentration Mass/volume standard

Made up to solvent volume

1 2:1-PI(1240 ng ML"*) 0.0124g 10 mL MeOH 2 2:l-PI(1012ng ^L'*) 0.0253g 25 mL MeOH 3 2:l-PI(112ng uL*) 0.0028g 25 mL MeOH 4 2:1-01(1044 ng ^L"*) 0.026 Ig 25 mL MeOH 5 2:1-01(104 ng ^ L ' ' ) 0.0026g 25 mL MeOH

6 2:1-PI (101 nguL' ' )

& 2:1-01(104 ng ^L"*)

1000 îL of standard 2 +

1000 of standard 4 10 mL propan-2-ol

3.2.4.2 Solid Phase extraction

Solid phase extraction was carried out using Isolute Si SPE cartridges (SPE 4-8) ( Ig silica

X 6mL, International Sorbent Technology, Hengoed, UK). A vacuum manifold extraction

system (Isolute, International Sorbent Technology, Hengoed, UK) at a flow rate of - I m L

min"' was used for elution. Samples for SPE were made up as described in Table 3.3.

Table 3.3 Samples prepared for solid-phase extraction

SPE Sample

Analyte and matrix concentration

Matrix spiked with standard (std, Table 3.2)

4 5 Mg2:l-PIgoil" ' 1 g crude oil + 4 | iL std. 1 5 1 ng2; l -PIgoi I" ' 1 g crude oil + 10 \xL std. 3

6 1 |ig2:l-PI and 1 2:1-01 g o i l ' 1 g crude oil + 10 ^ L std. 3 + 10 ^ L std. 5

7 1 Jig 2:1-PI and 1 ng 2:1 -01 mL hexane"

1 mL Hexane + 10 j iL std. 6

8 1 Mg2:l-PI and 10 Mg 2:1-01 g o i l " ' I g crude oil + 10 îL std. 3 + 10 ^ L std. 4

9 1 Mg2:l-PI and 10Mg2:l-OIgoil

1 g crude oil + 10 [iL std. 3 + 10 ^ L std. 4

45

3.2.4.3 Extraction procedure for samples SPE 4-6

Samples were diluted with ImL hexane emd transferred with a glass pipette on to SPE

columns (pre-washed with 7 ml hexane). Each sample vial was washed 4 times with 0.5mL

hexane and the washings transferred to the columns. The SPE columns were then eluted

with hexane (7 mL), diethyl ether (30 mL; SPE 6 and 7 were vacuum dried for a few

seconds) and propan-2-ol:ammonia (8:2 v/v, 10 mL). Each propan-2-ol:ammonia fraction

was blown dry under a nitrogen stream with heating to 60*'C.

The SPE 4 residue was reconstituted with 500 ^ L methanoLO. 1% TFA (v/v) whilst SPE 5

- 8 residues were reconstituted with 1000 f iL methanol:0.1% TFA (v/v). Each re-dissolved

residue was withdrawn from the vial into a ImL glass syringe and expelled through a

0.2^m PVDF syringe filter (Whatman, Maidstone, UK) into a 2mL glass auto-sampler

vial.

3.2.4.4 Extraction procedure samples SPE 9

A solid-phase extraction procedure currently used for commercial analysis of oils was

carried out ( Ig x 6mL SPE cartridge) as a comparison. The procedure is subject to

confidentiality agreement and cannot be disclosed. The SPE 9 residue was reconstituted

with 1000 ^ L methanoLO. 1% TFA (v/v) and filtered as above (section 3.2.4.3).

3.2.4.5 High Perfonmance Liquid Chromatography (HPLC)

HPLC was carried out using a P580A binary pump (Dionex-Softron GmbH, Germering,

Germany) at ImL min * flow rate and with a split of around 200 \xL (high pressure micro-

splitter valve, Upchurch Scientific Ltd., Oak Harbor, WA, USA) to the mass spectrometer.

All sample injections were 20 \xL except for analyses 1-4 of sample SPE 4 (Table 3.4)

were made with an ASH 00 autosampler (Dionex-Softron GmbH, Germering, Germany.

Elutions were carried out using the gradients shown in Tables 3.4 and 3.5 (solvent A,

46

MeOH:0.1% TFA v/v; and solvent B, 0.1% TFA in water v/v. A Hamilton PRP-1 reverse

phase column was used (5|im, 50 x 4.1mm Reno, CA, USA.).

Table 3.4 Elution gradients used for HPLC analysis of sample SPE 4 (solvent A,

methanol: 0.1% trifluoroacetic acid v/v and solvent B, 0.1% trifluoroacetic

acid in water v/v)

Analysis 1 Time (min) 0 0.1 15 25 30 40

5^L injection % A 70 70 95 95 100 100 5^L injection % B 30 30 5 5 0 0


5|iL injection % A 75 75 95 95 100 100 5|iL injection % B 25 25 5 5 0 0


5|iL injection % A 75 75 95 95 100 100 5|iL injection % B 25 25 5 5 0 0


20^L injection % A 75 75 95 95 100 100 20^L injection % B 25 25 5 5 0 0

Table 3.5 Elution gradient used for HPLC analysis of 5 ^ L injections of samples SPE

5-9 (solvent A, methanol: 0.1% trifluoroacetic acid v/v and solvent B, 0.1%

trifluoroacetic acid in water v/v)

Time (min) 0 0.1 17 27 28 35 % A 75 75 100 100 75 75 % B 25 25 0 0 25 25

3.2.4.6 Analysis of samples SPE 4-9 using HPLC/ESI-MS


(ThermoFinnigan, San Jose, CA, USA) ion trap mass spectrometer fitted with an

electrospray interface. Data were acquired and processed using Xcalibur 1.0 spl software

(ThermoFinnigan). Instrument tuning and mass calibration were carried out and checked 47

using the automatic calibration procedure (tuning and calibration solution; caffeine (Sigma,

St Louis, MO, USA), MRFA (Finnigan Mat, San Jose, CA, USA) and Ultramark

1621 (Lancaster Synthesis Inc, Widham, NH, USA) in methanol/water/acetic acid (50:50:1,

v/v/v)). Instrument method optimisation was carried out by infusing I M sodium acetate at

l ^ L min ' into a 200 jiL min"' eluent flow from the HPLC system by way of the built in

syringe pump, a Hamilton 1725N syringe (250 nL; Reno, CA, USA.) and a PEEK Tee

union (Upchurch Scientific Ltd., Oak Harbor, WA, USA). The automatic tune function

was used on a suitable sodium trifluoroacetate adduct ion. For the positive ion f i i l l scan

range m/z [100-1000], tuned on adduct ion m/z 563 the following instrument parameters

were used: source voltage, + 4.5 kV; capillary voltage + 20 V; tube lens offset, +10.00 V;

capillary temperature, 220 °C; nitrogen sheath gas flow rate, 60 (arbitrary units); and

nitrogen auxiliary gas 20 (arbitrary units). Data was processed and peak areas calculated

using the Qualitative programme in the Xcalibur 1.0 spl software. Extracted ion mass

chromatograms (EIC) were extracted from the ftdl scan; total ion chromatograms (TIC)

selected to m/z 0.1 and an isolation v^dth of m/z 1.


3.3.1 Thin layer chromatography (TLC)

As a first step in developing a method for the SPE of imidazoline corrosion inhibitor

compounds from crude oil, TLC of a Gullfaks crude oil and an imidazoline-based

corrosion inhibitor intermediate (CI-El) was investigated. TLC can provide a visual and

relatively simple method of investigating the chromatographic properties of compounds

using various solvent systems and stationary phases i f the analytes are amenable to a

convenient means of visualisation, such as fluorescence under ultra violet (UV) light or

48

reaction with a chemical reagent producing a coloured or contrasting reaction product. The

use of a Kieselguhr pre-concentration zone in the first 28 mm of a plate, allows large

volumes of dilute samples to be applied to the chromatographically inactive Kieselguhr

layer. On development the applied substances are concentrated in a band at the

Kieselguhr/silica interface from which chromatography starts to occur as normal.

TLC using a two-stage development on silica gel plates with a Kieselguhr pre-

concentration zone, similar to that described by Buck and Sudburywas carried out (TLC

1, Table 3.6), although visualisation was achieved using UV and iodine vapour and not the

SO3 charring used by the latter authors. Observation of the plate after development in

iodine vapour showed that most of the crude oil components had moved above the mid

point of the plate in a large tear drop spot with a black streak towards the diethyl ether

solvent front (Rf.êT 0.54-0.99, also visible to the naked eye and UV at 366 and 254 nm,

between developments). These components were moved during the diethyl ether first

development as they were clearly above the propan-2-ol (IPA):NH3 (8:2, v/v) second

development solvent front (Rf 0.50 relative to the first development). A faint spot

originating from the crude oil at Rf-ether 0.40 was also observed under UV at 366nm

between developments. Under UV at 366nm between developments there was faint

fluorescence at the origin of the CI-El sample and at the Kieselguhr/silica interface

indicating that there was some retention of CI-El components. Two faint spots at Rf-dher

0.57 and 0.73 originating from the CI-El sample were observed above the second

development solvent front. In the area of the second development, there were five spots

cleariy visible originating from the CI-El sample at Rf.iPA:NH3 0.04, 0.40, 0.47, 0.70 and

0.80. At the crude oil origin, grey spots remained with faint steaks towards the main spot.

When the procedure was repeated (TLC 2, Table 3.7), with the sample applied directly to

the silica zone of the plate, the Rf values for the crude oil and CI-El components were near

identical to those observed in TLC 1, except that an extra spot was present at Rf-[PA:NH3

49

0.40 on TLC 1. The spot at Rf.iPA:NH3 0.40 (TLC 1) may be accounted for i f the Kieselguhr

had resolved the components in the spot at Rf.iPA:NH3 0.51 on TLC 2. Promisingly and most

importantly, these initial results indicated that imidazoline compounds could be separated

from crude oil and a more detailed evaluation was undertaken.

Table 3.6 Thin layer chromatography Rf values for resolved crude oil and CI-EI

imidazoline inhibitor components (TLC 1). Conditions and procedure

described in experimental section 3.2

Sample Rf (First development, d iethyl ether) Crude oil Origin

(S) 0.40

(S-vf) 0.54-0.80

(S.d) 0.71-0.99 (SK,d)

Inhibitor CI-EI

0.57 (S,f)

0.73 ( s , 0

Rf (Second development, IPAcIVHa, (8:2 v/v)) Inhibitor CI-EI

0.04 (0.02) (S,d)

0.40 0.47 (S,d)

0.70 (S,d)

0.80

S = spot; SE = spot elongated; SK = streak; f = faint; v f = very

d = dark; vd = very dark; TdS = teardrop shaped spot;

366/254 = fluorescence under UV light at 366 or 254Tmi.

aint;



described in experimental section 3.2

Sample Rf (First deve opment, diethyl ether) Crude oil Origin

(S,) 0.43

(S,vf) 0.52-0.71

(S) 0.66-0.92

(SK) Inhibitor CI-EI

0.52 (S,0

0.67 (S,f)

Rf (Second develo pment, IPAiNHj , (8:2 v/v)) Inhibitor CI-EI

0.06 (S,d)

0.51 (S,d)

0.72 (S,d)

0.79 (S,d)

50

The TLC elution of crude oil and CI-El components by development in diethyl ether,

hexane and DCM solvents (TLC 3-5; Tables 3,8-3.10, respectively) was compared.

Developed in diethyl ether (TLC 3), the oil components eluted as a tear drop spot at Rf

values near identical to those in TLC 1. For Cl-El the origin was a very dark spot

indicating that most of the applied sample was not eluted. Two components at Rf-dher 0.54

and 0.67 were eluted, corresponding to spots in TLC 1, which was consistent with the

trimethyl benzene and naphtha components reported in the MSDS data provided. There

was a faint spot at Rfâ 0.03 which indicated the spot at Rf.iPA:NH3 0.04 ( R f ^ c r 0.02) on

TLC 1 was eluted by diethyl ether but not by IPA:NH3. Development in hexane (TLC 4)

showed no movement from the origin for CI-El except for a very faint spot at Rf-hexane

0.35, whilst the oil components were eluted from the origin to Rf-hexone 0.67 as a streak

comprising four distinct areas. Development of a plate with DCM (TLC 5) eluted crude oil

in a teardrop spot (Rf-ocM 0.62-0.87) similar to that observed in diethyl ether. The origin of

the crude oil spot was darker, indicating perhaps that not as many components were eluted.

There was also a streak from the origin to Rf-ocM 0.12. The CI-El origin was again very

dark, but there was also a light streak to Rf-[x;M 0.67. A faint spot was observed at Rf-ocM

0.73.

From the results of development of CI-El in diethyl ether, hexane and DCM it was found

that the imidazoline components were not moved from the origin whilst the trimethyl

benzene and naphtha components were. The crude oil components were eluted to varying

degrees by the three solvents, v^th hexane producing the widest spread of components and

diethyl ether the greatest elution with the least separation of components. To evaluate

solvent systems for eluting the imidazoline compounds and the asphaltene crude oil

compounds, diethyl ether was used as a first development stage to move the crude oil

components and trimethyl benzene and naphtha compounds from CI-El away from the

second development zone.

51



described in Experimental section 3.2

Sample Rf ( I development, diethyl ether) Crude oil Origin

(S) 0.54-0.72

(S,d) 0.71-0.97 (SK,d)

Inhibitor C l - E l

Origin (S, vd)

0.03 (S,0

0.54 (S,0

0.67




Sample F (Development, hexane) Crude oil Origin-0.14

(SK,d) Origin-0.35

(SK,366/254) 0.35-0.56

(SK) 0.57-0.67

(S) Inhibitor CI -EI

Origin (S, vd)

0.35 (S,vf)




Sample Rf (Development, DCM) Crude oil Origin

(S.d) Origin-0.12

(SK) 0.62-0.76

(S) 0.73-0.87

(SK) Inhibitor CI -EI

Origin (S, vd)

Origin-0.67 (SK,)

0.73 (S.O

52

Second development eluents (MeOHiNHa, 8:2 v/v; MeOH; IPA; MeOH:AcOH, 8:1 v/v;

TLC 6-9; Table 3.11-3.14 respectively) were evaluated to find a system that would allow

rapid elution of the imidazoline compounds. None of the above systems moved the crude

oil components remaining from the origin after the first development. MeOH:NH3 (8:2,

v/v) (TLC 6) elution produced greater resolution of CI-EI components and an extra spot

was detectable compared with that obtained using IPA:NH3 (8:2, v/v) (TLC 2). However,

some of the latter eluting components were not moved far from the origin. MeOH, IPA and

MeOH:AcOH (8:1. v/v) proved unsuitable as elution solvents as Cl-El components

remained at, or close to, the origin.

Table 3.11 Thin layer chromatography Rf values for resolved crude oil and Cl-EI



Sample Rf Tirst development, diethyl ether) Crude oil Origin

(S) 0.66-097

(TdS) Inhibitor CI-El

Origin (S)

0,51 (S.vf)

0.79 (S,vf)

Rf (Second development, MeOH:NH3, (8:2 v/v)) Inhibitor CI -E l

0.06 (S)

O.ll (S)

0.30 (SE)

0.50 (SE)

0.69 (S)

Table 3.12 Thin layer chromatography Rf values for resolved crude oil and Cl-El



Sample Rf (Firs [ development, diel hyl ether) Crude oil Origin

(S) 0.71-098

(TdS) Inhibitor CI -E l

Origin (S)

0.57 (S,vf)

0.86 (S.vf)

Rf (Second development, MeOH) Inhibitor CI -E l

Origin-0.13 (SK, vd)

0.34 (SK,d)

0.51 (S)

0.68 0.73

53




Sample Rf (First development, dietby ether) Crude oil Origin

(S) 0.77-0.98

(TdS) Inhibitor CI -El

Origin (S)

0.77 (S.vf)

0.93 (S,vf)

Rf (Second development, IP A) Inhibitor CI -El

Origin-0.15 (SIC, vd)

0.15-0.17 (SK, d)

0.69 (S,vf)

0.95 (S,vf)

Table 3.14 Thin layer chromatography Rf values for resolved crude oil and CI-El



Sample Rf (First development, diethyl ether) Crude oil Origin

(S) 0.66-0.98

(TdS) Inhibitor CI -E l

Origin (S)

0.61 (S,vf)

0.80 (S,vf)

Rf (Second development, MeOH:AcC m (8:1 v/v)) Inhibitor CI -E l

Origin-O.ll (SK, vd)

0.11-0.19 (SK, vd)

0.78 (S,f)

3.3.2 Infusion ESI-MS analysis of CI-El imidazoline corrosion inhibitor intermediate

Active compounds in the CI-El corrosion inhibitor product were determined by infusion

ESI-MS. Positive ESI spectra of CI-El in two solvent systems (1 ppm CI-El in

methanol:water, 7:3 v/v; and methanol:water:fonnic, 8:2:0.1 v/v/v) are shown in Figures

3.2 and 3.3. It is apparent from the spectra that the relative abundance maximum in the ion

54

current for the base peak (m/z 610.7) is higher in the methanoI:water:formic solvent system

than the methanol:water solvent (1.42E6 > 4.08E5). This is consistent with higher proton

concentration, owing to the presence of formic acid, leading to an increase in the number

of protonated molecular ions formed during ESI. It is also seen that the relative abundance

of m/z 348.5 is increased from -5% to ~ 25% in the presence of formic acid. The spectral

ion masses are similar to those shown by Gough and Langley,^^ for a TOFA/DETA

imidazoline product. The ion masses are consistent with the presence of oleic and linoleic

acid-derived imidazolines with so-called 2:1-imidazolines as the predominant compounds.

Further examination of the m/z values and relative responses of spectral peaks for the

methanol:water:formic acid system (Figure 3.3) showed that linoleic acid (Ci8:2) was the

main acid starting component {i.e. m/z 348.5 and 610.7) with oleic (Ci8:i) and hnolenic

(Ci8:3) acids also present (expanded regions of the spectra showing ions due to 2:1-

imidazoline and l:l-imidazoline are shown in Figures 3.4 & 3.5). Ions at m/z 374.5 and

636.7 indicated the presence of a C20:3 acid in the reactant fatty acids mixture. Tables 3.15

and 3.16 show m/z values for ions expected to arise from mass spectrometry of

combinations of various fatty acids used in the synthesis of 2:1-imidazoline and 1:1-

imidazolines. Evidence for monoamide and diamide precursors of imidazolines (or

hydrolysis products of imidazolines) could also be seen in the spectra {i.e. m/z 628.7 and

366.5) at ~ 50% abundance of the corresponding imidazoline-derived ions. Negative ion

ESI analysis of CI-El showed no peaks distinguishable from background.

55

NL; 4.08E5 + ESI m/z ( 50.00-1000.00]

100 -

90 z

80 -

70

§ 6 0

a " D C I 50

40

30

20

10

0

610.7

6087

160.9

129.0

115.0

100

175.0

612.7

636.7

P'^-^ 385 3

638.7

200 300 400 500 600 m/z

i|i I I nr.i^,y,,,T;y? , I |ni|,;i,i..'.|..J,..,,.i';,.-M' H,.^,i;i|i.i|L,,,,.Y 700 800 900 1000

Figure 3.2 Infiision positive ion ESI-MS mass spectrum of Ippm CI-El imidazoline

corrosion inhibitor in methanol:water (7:3 v/v).

NL: 1.42E6

100 -

90 ^

80 ~

70 -_

<a -c60 -"5 | 5 0 ^

I 4 0 -q :

| 5 0 ^

I 4 0 -q :

| 5 0 ^

I 4 0 -q :

30 -_

20 -j

10 -_

0 -

ESI m/z [50.00-1000.001

348.5

610.7

608.7_

606.7_ 350.5

346.4_ 180.7 392.4

6.12.7

636.7

638.7

912.8 11111 I I •i»»|r>ijT,.|...|.,.|..,,,..|.i,,...i.?.i. 1.1, .t..',|..'.|,??j,^,-.?7../,..n, Y

500 600 700 800 900 1000 m/z

Figure 3.3 Infusion positive ion ESI-MS mass spectrum of Ippm CI-El imidazoline

corrosion inhibitor in methanol:water:formic acid (8:2:0.1 v/v). 56

ESI m/z [50.00-1000.001 NL: 1.42E6

612.7

636.7

628.7

634.7

654.6 606.7

Figure 3.4 Expanded spectrum of m/z 600-670 region of Figure 3.2.

ESI m/z (50.00-1000.00] 348.5

NL:3.47E5

346.4

305.4 351.5

332.6

374.5

3766 392.4 388.4

330 340 350 360 370 380 390 m/z

400

Figure 3.5 Expanded spectrum of m/z 290-400 region of Figure 3.3.

57

Table 3.15 Calculated mono-isotopic masses for some Cis fatty acid-derived 2:1

imidazolines

0

1 Mono-isol opic masses for protonated 2:1 -imidazolines R1/R2 Ci7:l Ci7:2 C|7:3 C20:3 Cl7:| 614.6 612.6 610.6 638.6 Ci7:2 612.6 610.6 608.6 636.6 Ci7:3 610.6 608.6 606.6 634.6 C20:3 638.6 636.6 634.6 662.7

Table 3.16 Calculated mono-isotopic masses for some Ci8 fatty acid derived 1:1

imidazolines

H N y N ^

1 Ri Mono-isotopic masses for protonated l:l-imidazolines

R l Ci7:l C|7:2 Ci7:3 C20:3 350.5 348.5 346.5 374.5

3.3.3 Solid-phase extraction (SPE)

Following the results of the TLC analyses; (Section 3.3.1), a SPE system using columns

packed with silica gel was investigated to determine whether active corrosion inhibitor

components in CI-El could be retained and subsequently eluted without decomposition and

free from crude oil-derived interferents. The sequence of development of the SPE

procedures is outlined below.

3.3.3.1 Solid-phase extraction of CI-E1 (SPE 1)

A sample of CI-El was extracted as described previously (Section 3.2.3; SPEl). Hexane

and diethyl ether fractions were analysed by GC/MS whilst the IPA:NH4 eluent fraction

was analysed by ESI-MS. The ( J C / M S total ion chromatogram (TIC) of the hexane eluate

comprised early eluting volatile components (Figure 3.6).The components of the main

58

chromatographic peaks (e.g. Figure 3.7) were tentatively identified by comparison with the

online library (Chemstation software, Hewlett Packard) as a series of alkylbenzenes. The

GC/MS chromatogram (TIC) of the diethyl ether eluate indicated later eluting, higher

molecular weight components (Figure 3.8), which were tentatively identified from mass

spectra as originating from naphtha (e.g. Figure 3.9). Thus the components eluted by

hexane and diethyl ether were consistent with the designation of'trimethylbenzenes' and

'heavy aromatic naphtha' made in MSDS sheets accompanying the CI-El product.

Ik 0 lima

Figure 3.6

45:07 SS-39 13:33 24KW 34:36

GC/MS total ion chromatogram of the SPE hexane eluate from Cl-El

corrosion inhibitor.

^QQÂvPraypdScan:3TOtn670 710:12398 100 V, = 22537

90

w 70

P 50 I 40 < 30

119

91

51 „ 77

] j . j i , . y 105

148 J I r r I n r r i i i-i i i i i i i i i i i i i i i i i i T I i T i i i i i i i i i i i i -i i i i i i i i i n r i i i T i i i i r.

100 150 200 350 360 350 4(J0 ° "

Figure 3.7 Averaged mass spectrum of the major chromatographic peaks shown in

Figure 3.6.

59

100-90

8 Z t ™ 5 « § »

I 30 t- 20

10-

I

Figure 3.8

13:32

35 06

34:35 45:06 55:40

GC/MS total ion chromatogram of the diethyl ether SPE eluate from

corrosion inhibitor CI-EI.

?(iScia:2?83tt32î TIC: 107340 l W % = i Q »

1 0 ^ i : i

50

Figure 3.9 Averaged mass spectrum of the major chromatographic peaks shown in

Figure 3.8.

The ESI-MS positive ion mass spectrum of the first 3 mL of IPA:NH4 SPE eluate of CI-EI

(Figure 3.10), was similar to that of unfractionated product (Figures 3.2 and 3.3). The only

significant difference was in the relative abundances of the 1:1- and 2:1-imidazoline ions.

In the unfractionated product (Figure 3.3) m r 610.7 (2:1-imidazoline) is the base ion with

m z 348.5 ion (1:1-imidazoline) at ca 30 % relative abundance, whereas the m z 348.5 is

the base ion whilst the m r 610.7 is ca 70 % relative abundance. This may have been due to

60

partial fractionation of the 2:1- and l:l-imidazolines during elution. However, this could

not be confirmed as the second 5 mL IPA:NH4 eluent fraction was not analysed, as the

residue proved difficult to re-dissolve in IPA. The ion at m/i 388.5 was not observed in the

spectra of unfi^tionated CI-El (Figures 3.2 and 3.3). The spectrum does not indicate any

significant changes in the imidazoline/amide ratios (v/z no alterations in the ratios of ions

m/z 610.7 and 628.7) and therefore hydrolysis of the imidazoline components was

considered to be insignificant.

NL:1.29E6

100

90

80

70

§ 6 0 ^

+ ESI tnn [50.00-800.001 348.5

50 H

I 40 a:

30 -

20

10 -

348.5_

97.1 125.1 155.2

305.5

303.5 I

100 200 300

610.7

350.5

388.5

612.7

60a.7_

390.5

414.5

400 500

6 0 0 J _ J U f H i ^ ,690.8 750.7

600 800 m/z

Figure 3.10 Infusion positive ion ESI-MS full scan mass spectrum m/z [50-800] of the

propan-2-ol:ammonia eluent fraction (0-3mL) ft-om CI-El corrosion

inhibitor extraction SPE 1.

61

3.3.3.2 Crude oil and CI-E1 spiked crude oil solid-phase extraction (SPE 2 and 3)

A biodegraded North Sea crude oil from the Gullfaks Field^'** was extracted (Section

3.2.3; SPE 2) and the IPA;NH4 eluent fraction (0-6 mL) analysed by positive ion ESI-MS.

The mass spectrum of the crude oil eluate (Figure 3.11) contained a complex series of ions

in the range m/z 200-1400 with a base peak ion at m/z 607.7. No peaks at m/z values

corresponding to expected imidazoline or amides were detected.

The positive ion ESI-MS mass spectrum (Figure 3.12) of the IPAiNRj eluate (0-5 mL)

extracted from the same oil spiked with 2000 ppm CI-El (Section 3.2.3; SPE 3)

contained only ions due to the Cl-El product components (c/"Figures 3.2 and 3.3) and no

discernible interference ions from the constituents of the crude oil. Although the spectrum

was similar to that of unfractionated CI-El (Figures 3.2 and 3.3), the 2:l-imidazoline/l:l-

imidazoline relative ion abundances were approximately equal, whilst in the spectrum of

the same sample, analysed by flow injection ESI-MS the 2:l-imidazoline/l:l-imidazoline

relative ion abundances are approximately 2:1 (Figure 3.13).

ESI m/z \ 50.00-2000.00] NL: 1.33E4 607.7

779.8 593.5

397.5

3e4.7_ 369.5 309,3

265.5

980.8

1105.1

1143.7

200 400 600 800 ' 1000 1200 1400 1600 1800 2000 m/z

Figure 3.11 Infusion positive ion full scan mass spectrum m/z [50-2000] of the propan-

2-ol:ammonia SPE eluate (0-5mL) from Gullfaks crude oil (SPE 2).

62

1924.4

NL: 2.03E6

100

90

80

70

60

50

40

30

20

10 H

*ES\ m/z[ 50.00-2000]

348.5

305.5

140.1

303.5.

222.3 281.5

350.5

374.5

'i'"i"'T-n—r-"'i'"V|"'i—r—r 100 200 300

376.6 378.5

610.7

608.7_

L I! AD . 467.4 537.6 600.8

400 m/z

500

636.7

638.7

606.8^1 / l ^

600

Figure 3.12 Infusion positive ion full scan mass spectrum [m/z 50-800] of the propan-2

ol:ammonia eluate (0-6mL) extracted by SPE from Gullfaks crude oil

spiked with 2000 ppm CI-El (SPE 3).

63

NL: 5.55E5 100

100 -S c

90 i •o c <

eo i O a 9

70 -

§ 6 0 H

50

I 40 V 01 30 -

20 -

10

0

NL1.68E8

TIC MS

5.25

610.7

^12.7

rimefmin^ 10

608.7.

348.5

+ ESI m/z [150.00-1000]

RT:5.02-6.01

305.5

151.2

200

264J. 303.5.

350.6

374.6

376.5 606.7_

495.6 538.7 604 6

300 400 500 600

638.7

721.7 779.8

700 800 m/z

Figure 3.13 Flow injection positive ion full scan mass spectrum [m/z 50-800] (averaged

across peak) of the propan-2-ol:ammonia eluate (0-6mL) extracted by SPE

fi-om a 2000 ppm CI-El spiked crude oil (SPE 3). Insert shows the total ion

chromatogram of the 20 sample injection into a 150 min'* 90:10

propan-2-ol:water eluent.

3.3.3.3 Conclusions from the initial solid phase extractions

From the mass spectral analyses of the eluates of initial solid phase extractions of CI-El

and of crude oil spiked with CI-El at 2000 ppm, it can be concluded that the

imidazoline/amide components are initially retained on the SPE column and may be

readily separated ft-om the 'trimethylbenzene', 'naphtha' formulation components and fi-om

crude oil constituents, by sequential elution. Hydrocarbons are first eluted with hexane and

diethyl ether. The imidazoline/amide components could then be eluted with IPAiNHi,

blown down to dryness and re-dissolved in IPA without apparent decomposition or

64

interference from crude oil constituents at the nominal concentration of 2000ppm CI-El in

the crude oil. This is a significant advance on any method published hitherto.

However, the ratios of 2:1-imidazoline/1:1-imidazoline ion groups in the unfractionated

CI-El and the fraction obtained by SPE of spiked crude oil were different. For an

imidazoline produced by reaction of two parts of fatty acid to one part

diethylenetriamine," the 2:1-imidazoline ions (e.g. m/z 610.7) would be expected to be at

least twice as abundant as those of the l:l-imidazoline {e.g. m/z 348.5). Indeed, this was

seen in the mass spectra of unfiîctionated CI-El (Figures 3.2 and 3.3). However, in the

infrision ESI-MS spectra of IPA:NH4 eluates of SPE 1 & 3 (Figures 3.10 and 3.12) the ions

derived from l:l-imidazolines were as, or more abundant, than those arising from the 2:1-

imidazolines . Such differences in ratios were also observed between the infusion and flow

injection spectra of the same IPA:NH4 eluate of SPE 3 (Figure 3.12 & 3.13) and may be

attributable to instrument tuning and/or operating conditions. Differences in the MS

conditions and solvents were also shown to produce different ion ratios when

unfractionated CI-El was examined. The ESI-MS responses observed for the 2:1- and 1:1-

imidazolines were at least an order of magnitude greater when an inftision of acidified

methanol/water CI-El (Figure 3.3) was made, relative to an infusion in methanol/water

(Figure 3.2). A number of other factors may have contributed to the apparent differences

in 2:1-/1:1-imidazoline ion ratios. First, the volume of the IPA:NH4 eluates in each

fraction were not identical (SPE 1, 3 mL; SPE 3, 5 mL). Thus, different proportions of the

2:1-/1:1-imidazoline may have been eluted from each sample in these developmental

extractions. This was also consistent with the partial separations observed in the TLC

experiments. Second, the eluate from SPE 3 was not blown down to dryness and therefore

did not require resolvation, unlike that from SPE 1. Differential solubility may have altered

the ratios of the 2:1-/1:1 -imidazolines in SPE 1.

65

3.3.3.4 Solid Phase Extraction of palmitic and oleic imidazolines from crude oil and analysis

using HPLC/ESI-MS

To allow further development and optimisation of the SPE methods and to enable

quantitation, an HPLC/ESI-MS system utilising pure, single, authentic compounds was

needed. The use of HPLC should enable at least some separation of components, and

standardisation of the solvent system would allow the ESI-MS responses to be calibrated

for quantitative analyses. No literature detailing a HPLC/ESI-MS procedure for the

separation of imidazoline and their amide precursor/hydrolysis compounds could be found.

Although a reverse phase HPLC/ESI-MS procedure was used by Gough and Langley^^ for

the analysis of oilfield chemicals, no details of the stationary or liquid phases or operating

conditions were published. Development of a suitable HPLC system would also require

pure authentic compounds of known quality.

The complexity and the potential of developing an HPLC/ESI-MS system was

demonstrated by a preliminary investigation of CI-El components using a HyPurity

Advance column (Hypersil, Thermo-Hypersil, Runcorn, UK). Figure 3.14 shows the total

ion chromatogram of -200 ng CI-El injected on column, with isocratic elution

(methanol:water:formic, 70:30:0.1 v/v/v). A clear peak is seen at the solvent front (peak 1,

Figure 3.14) followed by numerous broad unresolved peaks. Ions at m/z values typical of

Ll-imidazolines and monoamides (111 and IV; Figure 3.1) were observed in the mass

spectra of scans across peak 1 {e.g. Figure 3.15). The co-elution of l:l-imidazolines and

monoamide components at, or close to, the solvent front was shown by the corresponding

extracted ion chromatograms {e.g. Figure 3.15). Mass spectra of peaks 2-5 (Figure 3.16)

showed m/z values corresponding to the main 2:1-imidazoline components. Extracted ion

chromatograms of the 2:l-imidazolines {m/z 608.7, 610.7, 612.7 and 614.7; Figure 3.17)

clearly corresponded to peaks 2-5 respectively and demonstrated separation of the

compounds. It was also apparent there was some separation of isomers as secondary peaks

could be distinguished, particularly for ions m/z 610.7, 612.7 and 614.7. The total ion and 66

extracted ion chromatogram peaks are very broad suggesting that there were several

competing interactions between the compounds and the solid phase and/or the solvent. As

a first trial the results were promising, showing that separation was possible and

compatible with ESI-MS detection. However, the complex nature of CI-El was evident

and due to the large number and unknown quantities of each component the product would

be unsuitable for ftirther development of the system.

100

95

9 0

85

80

8 C

75 CD

T ) C 70 Z3

Si 65

< 65

ive 60

*.< CD 5 5 0)

5 5

Q: 50

45

40

3 5

30

NL: 1.86E8 TIC ESI Full MS [50-1000]

30.14

44.74 35.69

50.84 55.19

t I I < I I I 1 I I I 1 I I I k I • t I t I I I I I I 1 1 j I I I I I I I I I I I I 1 I I I I I I I I I I I I ' I I I I j

0 5 10 15 2 0 2 5 30 35 40 45 50 5 5 60

Time (min)

Figure 3.14 HPLC/ESI-MS Total ion chromatogram of CI-El corrosion inhibitor.

HyPurity Advance column, 200 ng CI-El on column and isocratic elution

with methanol:water:formic 70:30:0.1 v/v/v (See text for details of peaks 1-

5).

67

100

100

2.34 NL: 1 22E7 m/z= 348 0-349 0

2 39 NL: 1 83E7 m/z= 366 0-367 0

10 20 Time (min) 40 50 60

0) ^ 100

366.3

160.9 348.5

175.0

4.0 146.9 214.0 . , , i >x . .1 . i . i i — L k4

368.3

392.3

394.3

200 400 600 800 m/z

1000

Figure 3.15 Extracted ion mass chromatograms of the main 1:1-imidazoline (m z 348.5)

and monoamide (mz 366.5) observed in CI-El and the mass spectrum of

peak 1 shown in Figure 3.14.

100

50

I 0

0 ?.100

50

0

608.6 160.9

175.0

634.6

m/z 500 1000

610.6

160.9 174.9

650.6

m/z 500 1000

100

50

612.7

160.9 174.9

• • H i l l

636.6

100

50

0

m/z

160.9

174.9

500 1000

614.6

662.6

m/z 500 1000

Figure 3.16 Positive ESI-MS mass spectra of peaks 2-5 shown in Figure 3.14.

100 - NL 1 33E7

SO

1676 q NL 1 33E7 A

/ V m/2 608.1-609 1

100 H NL 1 90E7 20 51

m/z=610 1-611 1 S 50 C

30.20 5 NL 2 10E7 m/2= 612.1-613.1 CD 0) 50 IT 36.83

^ NL 5 • 44.74

m/z= 614.2-615.2 50 30 18

• • ' ' I ' ' ' ' I ' ' ' ' I ' ' ' ' I ' ' ' ' I ' ' ' ' I 0 5 10 15 20 25 30 35 40 45 50 55 60

Time (mm)

Figure 3.17 Extracted ion mass chromatograms (from TIC Figure 3.14) of the main

2:1-imidazolines observed in CI-El: Top to bottom m z 608.7, 610.7,

612.7 and 614.7.

3.3.4 Authentic compounds

Oleic and palmitic acid-derived imidazolines compounds were synthesised and a

HPLC/ESI-MS system developed, simultaneously (Chapter 4). Indeed, an investigation of

the synthesis of imidazolines by thermal reaction of fatty acids with diethylenetriamine

was carried out as described in Chapter 4 and 5. 2:1-Oleic imidazoline (2:l-OI) was used

for further systematic investigation of the SPE extractions because it is known to be one of

the major components in imidazoline corrosion inhibitor products and indeed was observed

by ESI-MS of the CI-El product (Section 3.3.2). 2:1-Palmitic imidazoline (2:1-PI) was

chosen as an internal standard spike for quantitation because it is not present in the CI-El

product; the protonated molecular ion at m r 562.6 falls between that of the protonated Cis

1 :l-imidazoline/monamide and 2:l-imidazoline/diamide compounds, because it was

69

expected to behave in a somewhat physically and chemically similar manner to the major

Ci8 imidazoline compounds, and because palmitic acid is readily available at low cost.

Although deuterated analogues of analytes are conventionally used as internal standards

for mass spectral quantitation,*^ deuterated Ci8:i imidazoline was not chosen in the present

study as the molecular mass of a mono-deuterated OI would be isobaric with some of the

isotopic masses of imidazolines expected to be present in the commercial products. An

efficient synthesis of imidazolines was still to be determined and therefore the cost of

multi-deuterated analogues was prohibited

3.3.5 HPLC/ESI-MS

A reverse phase HPLC separation was developed using a gradient elution profile (Table

3.5) which allowed separation of the synthetic 2-alkylimidazolines, l:l-imidazolines, 2:1-

imidazolines, monoamides and diamides. For convenience the development of the

HPLC/ESl-MS method is discussed in conjunction with the imidazoline syntheses in

Chapter 4.

3.3.6 Solid-phase extraction of crude oil spiked with 2:]-paimitic imidazoline (2:1-PI;

SPE4andSPE5)

3.3.6.1 Solid-phase extraction of 2:1-palmitic imidazoline spiked crude oil

(S ig 2:1-Plgoir^ SPE 4)

A Middle East crude oil was supplied from an oilfield in which the drill well had been

treated ('squeezed')' v^th imidazoline-based corrosion inhibitors. A Ig sample of the oil

was spiked with 5^g (5ppm in oil) 2:1-PI as an internal standard, and extracted (Section

3.2.4; SPE 4). As this was a first extraction using commercial Isolute silica cartridges, the

70

volumes of eluate were determined by applying aliquots until hexane eluted with a light

yellow (9 mL) and diethyl ether with a very slight yellow colouration (30 mL). To ensure

elution of analytes the volume of eluent used was about five times the sorbent volume (10

mL). The dried IPAiNHs eluate was re-solvated in 500 0.1% TFA in methanol solvent,

equivalent to a two times pre-concentration. Since at this stage, the HPLC/ESI-MS method

was under development, the re-solvated extract was examined four times with small

changes in the gradient for the first three analyses and an increase in the injection volume

from 5 to 20 ^L for the fourth analysis (Table 3.2; Section 3.2.4.1). Positive ion ESI-MS

was carried out in full scan mode (m/z 100-1000) and selected ion monitoring mode (m/z

562.6 and 324.4).

The m/z 562.6 and m/z 324.4 selected ion monitoring (SIM) chromatograms showed peaks

at retention times expected for the 2:1-PI standard (R and Ri = C 1 5 H 3 1 , structure VIII,

Figure 3.1; Chapter 4 contains details of analysis and m/z values of 2:1-PI and 2:l-OI).

Single ion monitoring of m/z 324.4 for 1.1-Pl (R = C15H3U structure Vn, Figure 3.1) a

minor impurity in the 2:1-PI internal standard, showed small peaks with signal to noise

ratios of 2-3 and was therefore at the limit of detection. Extracted ion chromatograms

(EIC) for m/z 324.4 showed no peaks. Peak retention time, area, height and signal to noise

ratio for SIM and EIC of m/z 562.6 are presented in Tables 3.17 and 3.18. It was clear from

the peak area data that the change from 5 to 20 pL injections (analyses 3 and 4,

respectively; Table 3.17 and 3.18) resulted in a 2.5 times increase in response for both peak

area and height. It was also observed that SIM was twice as sensitive as the EIC for m/z

562.6.

71

Table 3.17 Peak data determined from HPLC/ESI-MS chromatograms of single ion

monitoring of m/z 562.6 (positive ion) for internal standard 2:1-palmitic imidazoline spiked

into crude oil (extraction SPE 4)

Single ion monil oring cbromatograms, m/z 562.6 Analysis Peak Retention

Time (min) Peak Area Peak Height Signal to Noise

Ratio 1 16.87 277607527 7643447 347 2 16.75 333322537 8734094 221 3 13.04 238168435 6695585 252 4 13.07 589072070 16916800 244

Table 3.18 Peak data determined from HPLC/ESI-MS extracted ion chromatograms of

m/z 562.6 (positive ion) for internal standard 2:1-palmitic imidazoline spiked into crude oil

(extraction SPE 4)

Extracted ion chromatog rams, m/z 562.6 Analysis Peak Retention


Ratio 1 16.92 141134837 4088380 61 2 16.73 169583445 4660826 87 3 13.05 130226114 3800347 107 4 13.06 313464454 9307471 63

Having confirmed that there was some recovery of the internal standard, m/z values

corresponding to the main Cis 2:1-imidazoline, l:l-imidazoline, diamides and

monoamides compounds were extracted from the full scan data. The only m/z values to

show evidence of a peak were at m/z 610.7, 612.7 and 614.7 (Figure 3.18). However, the

peaks were at the limit of detection with signal to noise ratios (S/N) of 8, 3 and 3,

respectively (Table 3.19). Analysing the mass spectra from these peaks (Figure 3.19),

indicated that the extracted ion m/z 614.7 (actual m/z extracted is ± m/z 0.4; Figure 3.18c;

for a Ci8:i/ Ci8:i 2:l-imidazoline), corresponded to the observed mass m/z 614.7 (Figure

3.19c). The observed m/z for the extracted ions m/z 612.7 and 610.7 peaks were m/z 612.0

and 610.0 respectively (Figure 3.19d and e), a significant m/z 0.7 difference. The generally

72

observed variation in m r values is normally ± m r 0.2, therefore, although the m r 612 and

610 peaks are at retention times estimated for Cisi / Ci82, Ci82 / Ci82 2:1-imidazoline,

there is considerable doubt over their identities. Indeed, when extracted ion chromatograms

of mz 612.0 and 610.0 were examined (Figure 3.20), identical retention times were

observed with an increase in peak area, height and signal to noise values (Table 3.19).

Extraction of ion chromatogram mz 614.0 (Figure 3.20) resulted in a small rise in the

base line noise at the same retention time (12.75 minutes) as /nr 612.0 and 610.0, but no

peak at the retention time observed for the extracted ion mz 614.7 (R, ^14.68 min). This

may suggest that the peak at mz 614.7 with a signal to noise ratio of 8, and a 2x pre-

concentration is evidence for a very low concentration of Ci81/ Cis i 2:1-imidazoline being

present in the sample.

100

50

100

50

0

100

50

4> •55 a. 50

100

5C

100

50

0

NL: 9 20E7 TIC + ESI m/z (100.00-1000 00)

RT: 13.06

i NL: 9.48E6 m/z- 562.1-563.1

c

RT: 14.68 NL: 5 12E5 m / z - 6 1 4 2-615 2

1 d RT 12 75 NL: 2.63E5

m/z- 612.2-613 2

e RT: 12.75

k NL: 8 58E5 m/z* 610 2-611 2

NL; 1.27E5

^ ' p m/z« 608 2-609 2

p M , . ' r ^ M . > p M f | . M f | f i r f | M . . J . . I t , I M f p i l f | > . . f y . f < > , . l l f p . f < r M n | M . i p . . . p i T . p . . . , . T M | . . . . J f . f . , M . . p M . , . M . | . . M , . ' « . . , . . M , . . . ) | , M M

10 15 Time (min)

2C 25

Figure3.18 HPLC/ESI-MS chromatograms of internal standard 2:l-palmitic

imidazoline (5 ig g oil*') spiked crude oil extraction SPE 4. a. Total ion chromatogram

{mz 100-1000), b. extracted ion chromatogram of internal standard (mz 562.6), c-f Main

Ci8 2:1-imidazoline corrosion inhibitor components {mz 614.7, 612.7, 610.7 and 608.7,

respectively).

73

100

50

0

562.6

: 176.4 2140 294.8 352.4 487.4

1563.6 609.8 747.0 790.9 846.7 974.8

100 ' t ' " i " 'T ' ^ i ' ' l " N ' " i ' ^ ' r " i ' " ' l i i ^ i r^ • rY ' ' ' t ^ ' ' ^ • ' ^ 'Nl^ 'X ' ' ' ' ' ' l ' ' ' ^ ' ^ ' 'T^ ' ' ' ' ' ' ' ' ' ' ' ' ' ' 1 ' ' ' 1 ' ^

200 300 400 500 600 700 800 900 1000 m/z

100 q

50 -

0

214.0

r 100

176.5

iVWih'.Vij»ii'>i|.'i

200

614.7 799.2

294.7 430.8 I 352.3

300

456.3 566.5

400 500 600 m/z

696.7 759.0

600 700 800

934.9 I

843.0

900

936.2

100

50

0

562.5

214.0 157.9

100 200

1000

d & e 610.0

kii-i 294.8 399.2 ^ ^ j ^ 546.4 658.4 747.0 846.1 974.5

300 400 500 600 700 800 900 1000 m/z

Figure 3.19 Mass spectra at the peak retention time, for peaks b, c and d/e shown in

Figure 3.18.


analysis 4 for internal standard 2:l-palmitic imidazoline spiked into crude

oil (extraction SPE 4)

Extracted ion c iromatograms of SPE 4, analysis 4 E I C m/z

Peak Retention Time (min)

Peak Area Peak Height Signal to Noise Ratio

614.7 14.68 19725010 439970 8 612.7 12.75 5162535 183293 3 610.7 12.75 23807243 765256 8

612.0 12.75 17061536 392760 10 610.0 12.75 48277662 1376148 24

74

100 - 3 NL 2 03E5

A A/ iiAI

1 r u . . . . . , . . v v w ^ 1 i ^ \ ^ v ^ y v w ^ ^ ^

rTVz=613 5-614 5

100 -1 NL 4 68E5

50

RT 12 75 m/z=611 5-6125

^ 1 0 o \ N L 1 4 a E 6 m/z=6O9 5-610 5

0 5 10 15 20 25 X Time (min)

Figure 3.20 HPLC/ESI-MS extracted ion chromatograms of crude oil extraction SPE 4.

Top to bottom, m r 614.0, 612.0 and 610.0.

3.3.6.2 Solid-phase extraction of 2:1-palmitic imidazoline spiked crude oil

(1 ng2:1-Plgoil SPE 5)

Following further developments in synthesising palmitic and oleic imidazoline standards, a

chromatographic gradient elution profile (Table 3.5) was developed that provided retention

and separation of the main compounds without excessive peak broadening for the diamides

observed in the synthesis of the standard compounds. This gradient was used for all

subsequent studies and allowed direct comparison between analyses. A separation of the

commercial inhibitor product CI-El was carried out (section 4.3.10; Chapter 4) and

provided retention data for the compounds, other than the standards, expected to be

observed in extractions of crude oil, i f present. This information was not available at the

time of the previous extraction {SPIi 4) and for the gradient used. A repeat extraction of

the crude oil spiked with the internal standard at lug g oil ' was carried out (Section

3.2.4.2; SPE 5). Again, recovery of the internal standard was observed, and peak retention

75

time, area, height and signal to noise ratios could be determined from the extracted ion

chromatograms of duplicate analyses of the extract (Table 3.20). Extracted ion

chromatograms of the main Cis compounds m/z values did not exhibit any peaks. However

a broad hump was observed in the base line for the main 2:l-imidazolines (Figure 3.21)

that was not seen in the equivalent solvent blank extracted ion chromatogram (Figure

3.22). The hump maximum responses were similar to the expected retention times for the

compounds. As the reconstituted extract was equivalent to the original sample (residue

made up to I mL), then compared to the previous extract {^PE 4(1 J) in which the response

for m/z 614.7 was close to the limit of detection, then no peak would be expected. The oil

for further spiking experiments was essentially Cis 2:1-imidazoline, l:l-imidazoline,

diamide and monoamide free.


m/z 562.6 (positive ion) for I ng g'* internal standard 2:1-PI spiked into

crude oil (SPE 5)



Ratio 1 14.44 28885000 1273951 33 2 14.47 42378559 1868293 29

76

100 N L 1 0 7 E 8

50

100 N L ; 1 . 9 7 E 6 ^

50

TIC m/z (100-10001

m/2= 562 1-563 1

I 1 0 0 ^ N L . 2 . 0 7 E 5

< u I 100 N L : 1 . 8 4 E 5 1^73

•5 50

m/z=614 2-615 2

nVz= 612 2-613 2

100 NL 2 35E5 ®5 16 92

50

1 0 0 ^ N L 1 9 1 E 5 13.90 14.47

50 .mHl^K m/z=608 2-609 2

U -p. .Tj>T?r|y^, , j r rfr[?r . . |rT 'n , . . . . , , ,M,,M>|. i . . | | n . . | i . . i | i • • • | . . . . | . . M | , , , , p .,,1 •••• , p , . . | . . . . , . , M | M T q n i i |

15 20 25 30 Time (min)

Figure 3.21 HPLC/ESI-MS chromatograms of internal standard 2:1-PI ( I f ig g" ) spiked

crude oil extraction SPE 5. a. Total ion chromatogram {m z 100-1000), b.

Extracted ion chromatogram of 2:1-palmitic imidazoline internal standard

( m r 562.6), c-f Main C i 8 2:1-imidazoline corrosion inhibitor components

{m z 614.7, 612.7, 610.7 and 608.7, respectively).

77

100 ^ ^ ^ ^ ^ ^ 1813 18 96 26 16 2673 J''^""'^'^'---— ^, TIC m/z (100-1000]

100 ^NL 24064 21 73 27 66 Ki'yk i L I! . A i L l . % \A m/z= 5621-563 1 50

8 irv? c 100 fviL 2 29E4 £^

^ " ' """""" I 100 -3 N L 2.2864 ^ ^ S ' '

2: 0

100 14 78 17 87 19 51 2519

( j - . . . i . ^ I m/z=6102-6112

100 ^ N L 2 9364

50

0

m/z= 608 2-609 2

fVlfTTlMftp...pM.|. Mp»..|.••.|M..,.M.,M..,...,,....JMM, MM,.. . . | . .p. . •,.M.p..,,....p...^....p.. 0 5 10 15 20 25 30

Time (min)

Figure 3.22 HPLC/ESI-MS chromatograms of solvent blank injection for crude oil

extraction SPE 5. a. Total ion chromatogram {mz 100-1000), b. Extracted

ion chromatogram of 2:1-palmitic imidazoline internal standard {m z 562.6),

c-f. Main Cig 2:1-imidazoline corrosion inhibitor components {mz 614.7,

612.7, 610.7 and 608.7, respectively).

3.3.6.3 Solid-phase extraction of crude oil spiked with 2:1-palmitic and 2:1-oleic

imidazolines (1 2:1-PI and 1 2:1-OI g SPE 6)

To further investigate the recovery, a Ig sample of the oil was spiked with 1 fig 2:1-

palmitic and 1 ^g 2:1-oleic imidazolines. The 1 ^g g ' of each component was used

initially because recovery of 2:1-palmitic imidazoline at the 1 ^g g oil"' was detected in the

previous extraction (SPE 5) and was detected at concentrations lower than established

methods. As no external calibration had been developed, a 1 îg mL"' solution made up

from the same standards used to spike the oil was analysed in order to provide a reference

response. The 1 mL re-solvated extracted residue was divided into two samples (SI, first

78

500^L and S2. remaining solution). The extracted ion chromatogram data acquired from

the extract samples 51, S2 and the standard are given in Table 3.21. Recovery of both 2:1-

palmitic and 2:1-oleic imidazoline was evident as observed by peaks at expected retention

times with expected m/z values. However, it was obvious that the response for 2:1-palmitic

imidazoline was greater than 2:1-oleic imidazoline. Relative to the standard, the peak area

for 2:l-palmitic imidazoline was 37% and 25% for sample SI and S2 respectively

compared to 4% and 2% for 2:l-oleic imidazoline fi-om the same samples. A decrease in

response was observed for sample S2 relative to sample SI , for 2:1-palmitic and 2:1-oleic

imidazoline (66% and 47 %, respectively). The extraction of both compounds was poor

compared to the standard response but recovery of 2:1-oleic imidazoline was extremely

low.

Table 3.21 Peak data determined fi-om FIPLC/ESI-MS extracted ion chromatograms of

m/z 562.6 and 614.7 (positive ion) for 2:1-PI and 2:1-01 spiked into crude

oil(l.12/1.04 Mgg"'oil)

Extracted ion chromatograms, m/z 562j 5 Analysis Peak Retention


Ratio Standard 14.96 178625276 5909611 225

SI 15.31 65863295 2708316 78 S2 14.72 43782861 1665033 69

Extracted ion chromatograms, m/z 614.7 Analysis Peak Retention


Ratio Standard 15.84 141509611 53533052 375

SI 16.16 6043503 228639 6 S2 15.64 2834681 123589 5

79

3.3.6.4 Solid-phase extraction of hexane spiked with 2:1-palmitic and 2:1-oleic imidazolines

(1 ng 2:1-PI and 1 ^g 2:1-01 mL' hexane; SPE 7)

To investigate the reasons for the poor recoveries and the difference between recovery of

2:1-palmitic and 2:1-oleic imidazolines, an extraction of spiked hexane was carried out

using the same procedure (Section 3.2.4.2; SPE 7). From the extracted ion chromatogram

data of a lug mL * standard and the extract (Table 3.22), a 42% and 24% area response of

the 2:l-palmitc and 2:l-oIeic imidazolines relative to the standard was observed

respectively. At 42% the increase in response for 2:l-palmitic imidazoline was small (5-

15%) compared to the extracted oil {SPE 6) and could easily have been attributable to

variations in instrumental or experimental conditions. The 24% response for 2:l-oleic

imidazoline was up to 20% greater than observed in the oil extraction. This would suggest

the oil matrix was affecting recovery of 2:1-oleic imidazoline to a greater extent than the

2:l-palmitic imidazoline compound. Although the recoveries were increased when a

refined solvent (hexane) was used compared to the crude oil, they were still less than 42%.

As one of the important physical properties of 2:1-imidazoline is strong sorption to

surfaces, particularly metallic surfaces, sorption to exposed metal surfaces may have

caused the loss of analytes. A stainless steel needle was used in the transfer of sample from

the vial containing the reconstituted extract residues to a glass syringe for expulsion

through a syringe filter (PVDF, polypropylene housing) and was considered likely to be

responsible for the loss of analytes. A simple test was carried out in which an auto sampler

vial containing I ^g mL"' each of 2:1-palmitic and 2:I-oleic imidazolines standards was

analysed and then transferred to another vial using the filtration method above. The result

(Table 3.23) shows a 39 % reduction in peak area for 2:1-palmitic imidazoline and 51 %

reduction for 2:1-oleic imidazoline. These were significant losses for a 1 ng mL"' standard.

A more detailed investigation would be required not only for the filtration procedure at

different concentrations but also for the sample vials used for preparation and collection,

and glass capillaries used for transfer of sample to the extraction cartridge. Teflon, plastic

80

or silanized glassware and equipment needs to be compared for sorption of analytes in

order to provide an optimum system for analyses.


m/z 562.6 and 614.7 for 2:1-PI and 2:1-01 spiked into hexane (1.01/1.04 ng

mL'' hexane)

Extracted ion chromatograms, m/z 562.6 Analysis Peak Retention


Ratio Standard 14.71 188930407 5978190 76

SI 14.76 79161052 2791403 205 Extracted ion chromatograms, m/z 614.7

Analysis Peak Retention Time (min)


Standard 15.68 211266279 6787619 186 81 15.66 51297101 1852033 105


m/z 562.6 and 614.7 for 2:1-PI and 2:1-01 standards before and after

filtration (1.01/1.04 ng mL"')

Extracted ion chromatograms, m/z 562.6 Analysis

1.01 ng mL*' Peak Retention


Ratio Unfiltered 14.95 262277819 8590937 89

Filtered 14.98 160170362 5828561 97 Extracted ion chromatograms, m/z 614.7

Analysis 1.04 pg mL''

Peak Retention Time (min)


Unfiltered 15.88 314545566 9884390 1653 Filtered 15.92 152762911 5171078 125

81

3.3.6.5 Comparison of solid-phase extraction methods for crude oil spiked with 2:1-palmitic

and 2:1-oleic imidazolines (1 2:1-PI and 10 ng 2:1-01 g oiP^ SPE 8 and 9)

To compare the extraction method being developed with a confidential SPE procedure

used for analyses of oils, extractions of oil samples spiked with 2:1-palmitic and 2:1-oleic

(1 ^g & 10 ^g g oil "*) were carried out using both methods. Comparison of the peak area

responses (Tables 3.24 and 3.25) indicates that the method being developed was 50% and

60% more efficient at extracting 2:1-palmitic and 2:1-oleic (average of duplicate analyses

of each extract).

Table 3.24 Peak data determined fi-om HPLC/ESI-MS extracted ion chromatograms of


oil(l.12/10.4 ^gg- )



Ratio SI 15.17 45322942 1928019 30 S2 15.10 43934279 1938563 53



Ratio SI 16.04 343452238 12767957 280 S2 16.02 355988605 12747084 306

Table 3.25 Peak data determined fi-om HPLC/ESI-MS extracted ion chromatograms of


oil (1.12/10.4 ^g g"') and extracted by a confidential SPE method

Extracted ion chromatog rams,/ra/z 562.6 Analysis Peak Retention


Ratio SI 14.79 20809552 860821 41 S2 14.75 24158678 1001944 44

Extracted ion cbromatog rams, m/z 614.7 Analysis Peak Retention


Ratio SI 15.69 148121788 5433384 196 S2 15.66 157185149 5539308 197

82

3.4 Conclusion

A semi-quantitative but sensitive and specific method, involving SPE followed by

HPLC/ESI-MS, has been developed for the determination of individual imidazolines at low

(<I0) parts per million concentrations in crude oils. Whilst the method requires further

optimisation due to the high experimental losses of imidazolines during work-up, it

nonetheless represents a considerable improvement on previous techniques and should

prove valuable for operational and environmental studies of corrosion inhibitor and

surfactant behaviour.

83

CHAPTER FOUR

Development of high performance liquid chromatography (HPLC)

separation of alkyl-imidazolines and amides with detection by

electrospray ionisation mass spectrometry (ESI-MS)

This chapter describes the development of high performance liquid chromatography

(HPLC) separation of alkyl-imidazolines and amides with detection by electrospray

ionisation mass spectrometry (ESl-MS). The synthesis of authentic palmitic and oleic 2:1

and 1:1-imidazoline is also described.

84

4.1 Introduction

Liquid chromatography (LC) with atmospheric pressure ionisation mass spectrometry

(API-MS) detection has been used for determination of many anionic, nonionic and

cationic surfactants in industrial waste waters, aquatic and marine waters.'* ' ''"' ^*^^"®'

However, there are relatively few reports of LC separation methods for alkyl-imidazolines

and related amides. ' ' ^ Neither are such compounds amenable to gas chromatographic

separation due to their high polarities and low volatilities. The lack of separation and

sensitive detection methods has made attempts to investigate the partitioning behaviour of

these compounds difficult.'*'

ESl-MS has been shown to be a powerful detection method for these compound types'' ' ^

(Chapter 2 and 3). However, flow injection ESI-MS does not allow for separation of the

individual components of products or of environmental extracts. A liquid chromatography

technique coupled to the ESl-MS detector would enable separation of the individual

components of imidazoline corrosion inhibitor products and interferences from co-

extracted compounds. The liquid chromatographic properties determined from HPLC

experiments might also be indicative of conditions needed for solid-phase extraction

absorbents and elution solvents for extraction of analytes from environmental waters such

as oilfield Produced Water and their discharges in the marine environment.

The aim of this investigation was therefore to develop a LC/ESI-MS method for the

separation and quantitation of alkyl-imidazoline and amide components of corrosion

inhibitors used in oilfield applications.

85

4.2 Experimental

4.2.1 Chemicals

Ultra pure water was obtained from an Elgastat filtration system (Elga, High Wycombe,

UK). A l l solvents used were HPLC grade except glass distilled diethylether (ether;

Rathbum Chemicals Ltd, Walkerbum. UK and BDH, Poole, UK). HyPersolv grade

methanol (MeOH), propan-2-ol (IPA), ammonia (0.88), trifluoroacetic acid (TFA), formic

acid and xylene (sodium-dried) were from BDH. Dichloromethane (DCM), ethanol

(EtOH), hexane, acetone and toluene were from Rathbum. Sodium acetate (AcNa, 99%)

was Aristar grade from BDH. Diethylenetriamine (DETA, 98.5%) and oleic acid (97%)

were supplied by ACROS Organics Ltd (Geel, Belgium). Heptafluorobutyric acid (99%),

palmitic and oleic acids (90%) were from Aldrich Chemical Company Inc. (Milwaukee,

WI, USA). The corrosion inhibitor intermediate product CI-El was from a commercial

supplier.

4.2.2 High performance liquid chromatography (HPLC)

HPLC was carried out using a P580A binary pump (Dionex-Softron GmbH, Germering,

Germany). ImL min * flow rate was split post column (high pressure micro-splitter valve;

Upchurch Scientific Ltd, Oak Harbor, WA, USA), with -200 ^ L min ' to the mass

spectrometer and the residue to a UV6000LP diode array detector (Thermoquest, San Jose,

CA,USA). 200 and 150 ^ L min ' flow rates used with 3mm and 2.1 mm diameter columns

were direct to the mass spectrometer. Sample injections (5 and 20 ^L) were made with an

ASI 100 autosampler (Dionex-Softron). HPLC columns investigated were; a stainless steel

column (3 x 100 nmi; Alltech Associates Applied Science Ltd, Camforth, UK.) packed

with Absorbosphere Cis (5^m; Alltech), amino-bonded Cg (Advance; 150 x 2.1, 3 ^m,

ThermoHypersil, Runcorn, UK), porous graphitic carbon (PGC; Hypersil Hypercarb, 100 x

86

2.1, 5 urn, ThermoHypersil), a stainless steel column (2.1 x 100 mm; Alltech) packed with

a hypercrosslinked polystyrene resin (MN200, 5^m; Purolite Int., Moscow, Russia) and

poly(styrene-divinylbenzene) (PRP-1; 50 x 4.1 mm, 5 \i, Hamilton, Reno, NA, USA).

Mobile phases, eluent compositions and gradient elution times are given in the text or with

the respective figures.

4.2 J Electrospray ionisation mass spectrometry (ESf-MST)

Mass spectrometry was carried out using a Finnigan Mat LCQ™ (ThermoFinnigan, San

Jose, CA, USA) ion trap mass spectrometer fitted with an electrospray interface. Data were

acquired and processed with Xcalibur 1.0 spl software. Instrument tuning, mass calibration

and data processing was carried out as described in Chapter 3 (Section 3.3.4.6). Selected

ion monitoring (SIM) was carried out using the SIM mode with the mass(es) selected to

m/z 0.1 and an isolation width of m/z 1. Extracted ion mass chromatograms (EIC) were

extracted from the ftill scan; total ion chromatograms (TIC) selected to m/z 0.1 and an

isolation width of m/z 1. Positive ion ESI-MS" was carried out as described in Chapter 2

(Section 2.2.2).

4.2,4 Fourier transform infrared (FT-IR) and 'H nuclear magnetic resonance (NMR)

spectroscopy

Fourier transform infi*ared (FT-IR) spectroscopy was carried out on a Bruker FT-IR IFS66

spectrometer (Bruker Inc, USA) and data acquired with OPUS 2.0 Optics software

(Bruker, Inc). Samples were prepared as KBr disk. *H nuclear magnetic resonance (NMR)

spectroscopy was carried out on a JEOL EX-270 FT-NMR spectrometer. Samples (10-20

mg mL' ') were dissolved in C D C I 3 .

87

4.2.5 Imidazoline synthesis procedures

4.2.5.1 2:1 Thermal reaction of oleic acid with diethylenetriamine

Oleic acid (2.48g, 8.8 m mole, 97 % Acros) was heated in a three neck, round bottom flask

(50 mL). A thermometer was fitted through a side neck and positioned in the reaction

mixture above the Teflon coated magnetic stirring flea. The top neck was open to the

atmosphere, whilst the second side neck was stoppered after addition of DETA. The

mixture was heated to 45°C whilst stirring. DETA (0.53g, 5.1 m mole) was added drop

wise {ca 10 mins). The temperature rose to 60°C as a clear, gel like soap was formed. This

became liquid on heating to 105**C and steam was evolved. The solution was heated to

155°C over 35 minutes and continued for 240 minutes. The reaction mixture was allowed

to cool. A side condenser was fitted to the top neck, and a vacuum was then applied (the

reaction mixture erupted around the flask on initial application of vacuum). The reaction

mixture was heated to 160°C at - 0.5 Ton* and heating continued for 120 minutes. On

stopping the reaction, condensation and dark brown oily spots were visible on the side of

the reaction flask above the surface of a dark yellow oil product. After cooling overnight

the reaction flask was stoppered. A yellow waxy material and dark brown spots were

visible on the flask wall above a viscous dark yellow oil product. After four days storage in

the flask at room temperature a waxy yellow solid was visible around the flask and into the

viscous oil. An aliquot of the oil was taken up in a glass Pasteur pipette and 0.0158 g

transferred to a glass volumetric flask and made up to 10 mL with methanol (Sample O I / l ,

1.58 mg mL"'). The reaction flask was heated tol85°C. The yellow oil became darker on

heating and over ca 2h became dark brown in colour. A temperature of 185 °C was

maintained for 24 hours. On cooling a black, tar-like substance was produced. Product

(0.0051 g) was transferred to a 7 mL glass vial and IPA (5 mL) added by auto-pipette

(sample 01/2, 1.02 mg mU').

88

4.2.5.2 HPLC/UV analysis of 2:1-oleic imidazoline synthesis product (sample 01/1)

An isocratic elution was carried out on Cis reverse phase column (Absorbosphere Cis) with

an 80:20 % A:B eluent at a flow rate of 200 îL min ' \ Eluent A, 1% acetic acid in

methanol (v/v) and B. water:methanol:acetic acid (90:10:1 %, v/v/v). UV detection was

carried out in the range 190-360 nm and at a discrete 230 nm wave length. No signal was

observed for 5 ^ L injections of 10 and 100 x dilutions (in 2:1 A:B)of the sample 01/1.

4.2.5.3 2:1 Themial reaction of palmitic acid with diethylenetriamine reflux in xylene

A 2:1-palmitic imidazoline was synthesised by Mr. Andrew Tonkin (laboratory technician.

University of Plymouth, UK). Palmitic acid (5.12g, 20 m mole) was reacted with DETA

(10 m moles, 1.08 cm^) by refluxing in xylene (l60mL) 144 -145°C, and water (0.36 c m \

66%) removed azeotropically by way of a Dean and Stark apparatus. The reaction was

stopped after 144 hours when no further water could be collected. Sub samples were

removed at intervals (7, 23, 30, 47 and 71 hours) using a syringe and PTFE tubeing. After

stopping the reaction, a white precipitate started to form at room temperature and settled

out over 24 hours. Xylene was removed by rotary evaporation. The crude product was re-

crystallised in acetone to yield 4.28g (76%) white powder, m.p. 81°C (lit. m.p. 78-79 °C,^^

m.p. 85-87 ""C xylene solvent synthesis^^ and m.p. 80-82 ''C solid-phase synthesis^^). FT

IR spectrum (u/cm ' ) : 1643, 1550 (-NH-C=0), 1608 (C=N) (Appended; Figure A . l ; FTIR

discussed in Chapter 5, Section 5.3 4). The sub samples where blown dry with nitrogen.

Stock solutions of each sub sample were prepared by dissolving (1.4 mg 7 hr, 1.6 mg 23

hr, 1.2 mg 30 hr, 1.4 mg 47 hr and 1.2 mg 71 hr) in 1000 ^ L methanol (samples Pl/1-

7hr/23hr/30hr/47hr and 71 hr respectively). The final product (11.2 mg) was made up to 10

mL with methanol (Sample Pl/l-fp). A 1000 ^ L methanol blank was prepared. Stock

solutions where diluted as required (e.g. for a 10 x dilution; 100 îL of each stock solution

was diluted 10 times by adding to 900 ^ L methanol:water:TFA (80:20:0.1% v/v/v)).

89

Serially diluted standards (0.0001 to 100 ^g mL' ' ; 0.0124 to 124 ^g mL * and 0.062 to 62.0

Hg mL"^) foT HPLC/ESI-MS response were prepared.

4.2.5.4 1:1 Thermal reaction of oleic acid with diethylenetriamine in xylene

A 1:1 molar ratio synthesis of oleic acid with diethylenetriamine in xylene was carried out

as described for 2:1-PI (Section 4.2.4.3), by reacting oleic acid (8.47 g, 30 m mole, 90 %

Aldrich) with DETA (3.2 g, 31 m mole) for 91 hours. Aliquots where taken at 1, 3, 19 and

91 hours and blown down with N2 with heating to 50 **C.

Stock solutions of each sample were prepared by weighing out (0.0259 g 1 hr, 0.0277 g 3

hr, 0.0261 g 19 hr and 0.0252 g 91 hr) and making up to 25 mL with ethanol in a glass

volumetric flask (Samples OI/2-lhr/3hr/19hr and 91hr respectively). 100 x dilutions for

HPLC/ESI-MS analysis were prepared by transferring 10 ^ L to 990 îL of required

solvent.

4.2.5.5 2:1 Thermal reaction of oleic acid with diethylenetriamine in xylene

A 2:1 molar ratio synthesis of oleic acid with diethylenetriamine in xylene was carried out

as described above, by reacting oleic acid (100 g, 350 m mole, 90 % Aldrich) in 200 mL

in xylene with DETA (18 g, 175 m mole) for 95 hours. After 2 hours, there were two

layers visible in the trap, a cloudy white lower and clear upper layer. The trap contents (9

mL), containing both layers was transferred to a 10 mL measuring cylinder. This on

cooling separated to two clear layers (ca. 4 mL lower water layer). At 5 hours a further 4

mL lower water layer was visible in the trap. After 95 hours excess xylene was removed by

opening the drain tap on the Dean and Stark trap, preventing condensed xylene from

returning to the reaction flask. Heating was stopped after 20 minutes when the temperature

rose fi-om 149 to 160 °C. 9 mL of water was collected via the Dean and Stark trap (95 % ) .

Aliquots of the reaction solution (-2 mL) where taken at 5, 23 and 95 hours. The golden

brown, viscous oil product (sample 01/3) was stoppered and sealed on cooling to room 90

temperature and stored at 4**C. Xylene was removed from the sub-samples by rotary

evaporation with heating to 100**C in a water bath. The 23hr sub-sample on cooling

contained white precipitate on the flask wall and was the result of hydrolysis to the product

amide, due to steam from the water bath entering the flask under vacuum due to a poor

seal.

Stock solutions of each sample were prepared by weighing out (0.0270 g 5 hr, 0.0264 g 23

hr and 0.0271 g 95 hr) and making up to 25 mL with methanol in a glass volumetric flask

(Samples OI/3-5hr/23hr and 95hr respectively). 100 x dilutions for HPLC/ESI-MS analysis

were prepared by transferring 10 to 990 of required solvent. Calibration standards

(0.005 - 10 ^g mL"') were prepared by sequential dilution in 0.1% TFA in methanol of a

1008 \ig mL"' 2:1 -01 stock solution (0.0252 g 01/3 up to 25 mL methanol).

4.2.5.6 Vacuum distillation of 95 hour reaction product

The 95 hour 2:1 product (63.9 g) was vacuum distilled by way of a condenser and a three

way trap. A clear fraction (xylene) was collected (27^C at 2 mm Hg). The temperature rose

to 140°C, (0.8 mm Hg) as a white vapour was observed. Clear yellow oil started

condensing out (fraction 2). This continued as the temperature rose slowly to 160°C. It

became apparent that air was being drawn in around the top of the condenser and could not

be sealed. The temperature rose to 2\2°C and the oil started solidifying (white) as it

reached the collection flask. Changed to the third collection flask, temperature dropped and

rose as air leak sealed and unsealed as darker oil was condensing out and solidifying.

Heating and vacuum was stopped. On cooling the remaining oil was a dark black, very

sticky semi-solid.

91


In order to develop an efficient HPLC/ESI-MS separation and detection method for

imidazoline compounds, authentic compounds of known composition were required As no

commercial authentic compounds were available, synthesis of representative compounds

was required. Since it is one of the major components of commercial corrosion inhibitor

products, 2:l-0leic imidazoline (2:1-01; structure VI I I , R and Ri = C17H33, Figure 3.1) was

chosen as an initial synthetic target. An internal standard was also required to enable

quantitation of extraction methods of real samples. 2:1-Palmitic imidazoline (2:1-PI;

structure V n i , R and Ri = C15H31, Figure 3.1) was not observed in any of the commercial

products previously analysed (Chapters 2 and 3), and was thought to be a reasonable

surrogate. The mass to charge ratio of the protonated 2:l-palmitic imidazoline ion (m/z

562.6) falls between those of the major 1:1 and 2:1-imidazoline components (1:1-01 m/z

350.4 and 2:1-01 m/z 614.6) and thus would not be expected to cause interferences in

mass chromatography. A di-deuterated 2:l-oleic imidazoline would not be as suitable as it

would be isobaric with 2:l-stearic imidazoline (structure VII I , R and Ri = C17H35, Figure

3.1, m/z 618.7) whilst a mono-deuterated analogue would be isobaric with the '^C masses.

A review of published methods of imidazoline synthesis''*''^'^'^ revealed that rather

surprisingly, although the synthesis of imidazolines has been known since at least 1888,*°*

there is no well-accepted synthetic method and much confusion remains over the exact

mechanisms operating. Both solid-phase and solvent/reflux methods combining selected

amines with fatty acids, have been employed in the literature. Figure 4.1 shows the various

intermediates and pathways proposed for thermal syntheses of 2:1-imidazolines and are

discussed in detail in Chapter 5. Therefore it was decided that both solid-phase and

solvent/reflux methods would be investigated for the production of pure imidazolines.

92

I R H : H,N-

OH

Amine salt/Soap

o I

^ H 3 N : V And/Or

0 I V

^NH2

V I H,N.

V H Y

Pathway 1

R r ^ o °

And/Or

H 0

V I I I

A Pathway 2

R

•NH2 V I I

O R ^ f I

OH

Figure 4.1 Proposed reaction pathways for the thermal condensation reaction of fatty

acids with diethylenetriamine. Naming as Figure 3.1.

93

4.3,1 Solid-phase synthesis of 2:1-oleic imidazoline

A solid-phase thermal condensation synthesis of 2:1-oleic imidazoline based on the

method described by Bistline et. was carried out. The reaction proceeded as described

(Section 4.2.5.1) without problem. However, after four days the yellow waxy substance

observed on the flask wall of the product had visibly increased in amount at the oil/flask

surface. It was thought this was the diamide (either structure V or VTI, Figure 3.1)

hydrolysis product.^*" After removal of an aliquot of the oil product (Sample 01/1;

Section 4.2.5.1), the reaction mixture was ftirther heated (185*'C) for 24 hrs to observe i f

the waxy material re-condensed. On cooling, after 24 hours the product was a black tar-like

substance.

Infusion positive ESI-MS analysis of the original yellow oil (Sample OI / l : Figure 4.2),

shows a base peak ion at m/z 614.7 consistent with the presence of a protonated 2:l-oIeic

imidazoline. The only other ion of significance in the spectrum was m/z 307.5 (5%) which

was attributed to a protonated 2-oleic imidazoline (structure EX, Figure 3.1). It was unclear

whether this was due to in-source fragmentation of 2:l-oleic imidazoline (Augmentation

during the electrospray process) or to the presence of protonated 2-oleic imidazoline. The

latter is a known Augmentation ion of the 1:1- and 2:1-imidazolines (Chapter 2; Section

2.). There was a very small ion at m/z 350.6 (-1%) attributed to the protonated l:l-oIeic

imidazoline. The mass spectrum suggested that the product was reasonably pure (ca 95%).

The reheated final product was also analysed by flow injection positive ion ESI-MS

(sample 01/2; Figure 4.3). The base peak m/z 612.6 showed a loss of 2 Daltons (Da) from

the molecular mass of the protonated 2:1-Oleic imidazoline ion attributed to loss of H2.

Further ESI-MS analysis was not carried out on this product to prevent instrument

contamination as it was difficult to remove residues from the ESI source and the priority at

this stage of the research was to develop a HPLC/ESI-MS method. It was noted however

94

that m/r 612 is a common mass observed in imidazoline products and has previously been

assigned to 2:l-oleic/linoleic imidazolines by multistage mass spectrometry (MS°) (see

Chapter 2 and 3) and would imply loss of H2 from an alkyi group. However, MS° was not

carried out and the m/z 2 loss may be loss of H2 from the imidazoline moiety to give an

aromatic imidazole.

80

72 a

64

56

a 40

32

24

16

307.5

308.5

| i r i i | n n | i i r i [ f i i i | i i i m i m M i 306 308 310

flVz

614.7-

615.5

305.6

614.7

| i i i i | r i i ' r | T n i i i i i i | i i i i | i r i i | i i i i | i M i | i i i 612 614 61S 618

mft

615.5

' I I " 80 160

I I " 240 320 400 ' 4 8 0 5 6 0 ' 640 720 geo

Figure 4.2 Positive ion ESI mass spectrum of 2:1-oleic imidazoline synthesis product

sample OI / l . Infusion at 3 ^ L min"', Full scan m/z [50-2000].

95

96

80

72

64

I 56

I 46 J on 40

32

24

16

612.6 612.6

613.6 o 614.5

| i i r i | i i r i | I I I | i i i r | i i i i | r r i I 611 612 613 614 615 618 617

237.1

•613.6

859.2 831.2

811.2

te.ili..„ajl

860.2 873.2

1-874.2 •887.2

' • • • • I • • • • | M M | I I I I M I M I I I I | I I I I M I I I | I I I 1 1 1 1 1 I

160 240 320 400 480 560 640 720 800 880 960

Figure 4.3 Flow injection positive ion ESI mass spectrum of 2:1- oleic imidazoline

synthesis product sample 01/2. 5 Injection via "T" connection into 150

\iL min* 0.1% TFA in MeOH, fl i l l scan m/z [100-1000].

4.3.2 Synthesis of 2:1-palmitic imidazoline by Dean and Stark reflux in xylene

Apart from the solid state reaction method outlined above, imidazolines have also been

prepared by heating the reagents in solvents (e.g. Butler and O'Regan,^^ Maddox"). Often

the latter methods have employed azeotropic removal of water produced in the reaction

with toluene.^' Azeotropic removal of water is a simple method of removing water of

reaction whilst maintaining a constant temperature. The reagents are refluxed in a suitable

solvent which forms an azeotrope with water in a flask fitted with a Dean and Stark trap

and condenser (Figure 4.4). The azeotrope vapour condenses and runs back into the trap

were the heavier water separates out and remains in the trap whist excess solvent returns to

the reaction flask. The trap should ideally be fitted with a drain tap to allow collected water

to be removed i f the volume exceeds that of the trap. It was thought that i f a Dean and

Stark method worked, it would provide a simple one-pot synthesis without the requirement

96

of high temperatures and reduced pressure. 2:1-Palmitic imidazoline was prepared by way

of a Dean and stark reflux in xylene (mixed isomers) which boils at 144-145°C and forms

an azeotrope with water (Section 4.2.4.4). The reaction was monitored by analysis of sub-

samples of the reaction solution taken at 7 and 47 hours for flow injection ESI-MS. The

mass spectrum for the 7 hour sample (Figure 4.5) showed two main ions; m/z 324.4 as the

base ion and m/z 562.6 (28%). The masses are consistent with 1:1-PI {m/z 324.4; structure

VTJ, R = Ci5H3i. Figure 3.1) and 2:1-P1 (m/z 562.6; structure VI I I , R and Ri = C15H31,

Figure 3.1). For the 47 hour sample (Figure 4.6) the major ions were m/z 562.6 (100%) and

m/z 324.4 (49%). No ions due to DETA, palmitic acid, monoamide or diamide starting

products or possible intermediates were detected. Between 7 and 47 hours the 2:1-PI

increased relative to 1:1-PI and the postulated intermediate amides were not observed. Of

the theoretical yield of water, 66% was collected in the trap. This low yield of water was

probably mostly due to loss of vapour during collection of the sub-samples.

Thermometer

Heater

Condenser

Dean and Startt trap

Two-neck round-bottom flask

Figure 4.4 Apparatus and setup used for xylene reflux synthesis of imidazolines using

a Dean and stark trap.

97

100

80

80

70

^ 60

50

40

30

20

10

1 CO

240 400 480 560 mft

640 720 'So' I 960

Figure 4.5 Flow injection positive ion ESI mass spectrum of 2:l-palmitic imidazoline

synthesis product sample PI/l-7hr. 5 ^ L Injection via "T" connection into

150 ^ L min"' 0.1% TFA in MeOH, full scan m/z [100-1000].

72 J

f 64 J

56 J

elaUv

t 48 J

40 J

32 J

24 J

16 J

8 ;

324.4 n

237.1 158.9

I I. i

430.9-

562.5-

544.7- 563.5 702.5 1 '''-'rV^ 974.5,

160 240 320 400 480 560 640 720 800 880 960

Figure 4.6 Flow injection positive ion ESI mass spectrum of 2:1-palmitic imidazoline

synthesis product sample PI/MThr. 5 ^ L Injection via "T" connection into

150 nL m i n ' 0.1% TFA in MeOH, full scan m/z [100-1000].

98

4.3.3 Investigation of the HPLC separation, UV and ESI-MS detection of2:I-OI

There are few HPLC methods for the separation of imidazolines and related amides. * ' ^

Gough and Langley^^ reported the use of reverse-phase HPLC/LTV and ESI-MS for

commercial imidazolines added to production fluids. However, no HPLC column phase or

eluent details were given. They reported HPLC/UV (230 nm) calibrations of an

imidazoline/quat corrosion inhibitor standard in the range 50-250 ppm. A reverse-phase

HPLC/refi^ctive index (RI) method for the separation of imidazolines from their diamides,

was reported by Hampson et. al.^. The method described was for short chain fatty acid

(C9-C12) derived imidazoline and diamides using an octadecyl bonded silica phase and

isocratic methanol:0.1 N acetic acid eluents (70:30-90:10 v/v). The refractive index

detection was not very sensitive with "barely detectable peak heights" for 40 ng 200 ^L• '

(200 ppm) injections of pelagonic acid (nonanoic acid) derived 2:1-imidazoline and

diamide. A HPLC/UV (192-360 nm, photo-diode array detector (PDA)) analysis of the

2:l-OI based on that described by Hampson et. al.,^^ was carried out on a Cis reverse-

phase with isocratic methanol:water:acetic acid (82:18:1 v/v/v) elution (Section 4.2.4.3).

No significant UV signal was observed for 158 ^g mL"*, 5 | iL injections even when the

eluent was switched to 100% methanol:l% acetic acid after 30 minutes. As an imidazoline

based product (CI-El) had previously been analysed by HPLC/ESI-MS herein (Chapter 3;

Section 3.3.4) and separation demonstrated on an amino-bonded Cg phase (HyPurity

Advance, Hypersil) no further analysis were carried out on the Cig phase herein .

The HPLC/ESI-MS separation of the CI-El imidazoline product on Hypersil Advance®

column, (Discussed in Chapter 3; Section 3.3.4) produced very broad peaks for the

imidazoline components (Figures 3.14 - 3.17; Chapter 3), suggesting several competing

interactions between the compounds and the solid-phase, stainless-steel column

components and/or eluents. The imidazolines and amides are basic and readily protonate in

solution to give a hydrophilic cationic species which with the hydrophobic non-polar alkyi

99

moieties, give competing interactions and a surface-active nature. The alkyl moieties will

have strong interactions with alkyl groups on chromatographic phases, such as Cis and Cg

bonded silica, whilst the protonated sites will interact with the un-bonded silano! sites. The

surface active nature can have interactions with the stainless-steel column and fittings. It

was thought that an ion-pair modified eluent might alleviate the ionic and surface active

interactions. Polymeric resin chromatographic phases such as polystyrene-divinylbenzene

are generally more tolerant of wide pH ranges (pH 1-14) than bonded silica (pH 2-7), and

are more tolerant of ion-pair reagents and have strong reverse-phase interactions for many

polar compounds. A Hamilton PRP-1 (5 1 poly(styrene-divinylbenzene)) column (50 x 4.1

mm) was therefore investigated with trifluoroacetic acid (TFA) as an ion-pair reagent for

the retention of 2:1-01.

Extracted ion chromatograms (EIC) fi-om an initial isocratic elution of 2:1-01 on PRP-1

with 0.1% TFA in methanol (Figure 4.7), showed that 2:1-01 (m/z 614.7; t = 0.66 min)

eluted close to the solvent front (to = 0.43 min) with a capacity factor (k) of 0.5, and very

little peak tailing. It was also observed that an m/z 307.5 ion elutes on the solvent front

0.43 min, k = 0) with a smaller peak at k 0.5 (0.66 min), directly under the 2:1-01 peak.

This shows that 2-oleic imidazoline (01, structure EX, R = C17H33; Figure 3.1) is present in

the sample as the peak at k = 0 and is the result of ESI source fragmentation of the 2: l-OI

precursor ion. To increase retention of 01 and resolution from 2:1-01, an isocratic elution

with 0.1% TFA in methanol:water (90:10 v/v) was carried out (Figure 4.8). This resulted in

a sharp peak for 01 at k = 0.4 and a very broad peak for 2:1 -OI between k = 13-64. In order

to improve the 2:1-01 peak, gradient elutions of 0.1% TFA in methanol (eluent A) 0.1%

TFA (eluent B) were investigated For the gradients [(time/%A) 0/70-1/70-15/100 and

0/80-1/80-15/100] (Figures 4.9 and 4.10 respectively), the 2:1-01 peaks are sharp with

little tailing and well resolved from 1:1-01 and 01. Changing the eluent starting

composition from 70 to 80% A, had a larger effect on the retention of both 1:1-01 (5.64 to

100

1.75 min) and 01 (9.50 to 5.05 min) compared to 2:l-OI (16.03 to 14.68 min). Both

gradients produced good baseline resolution and good peak shapes for the three

components of the 2:1-01 synthesis products and showed that PRP-1 was a suitable

chromatographic phase for separation of 2:1-01, 1:l-Ol and 01 from each other

100

50

0.66

0.43

50 0.66

0 100

50

0 66

B

NL: 485E7 TIC

NL: 651E5 m/z = 307.0-3080

NL: 2 86E7 m/z = 614.2-6152

4 6 Time (min)

8 10

Figure 4.7 HPLC/ESI-MS mass chromatograms of 2:1-oleic imidazoline product by

isocratic elution with 0.1% TFA in methanol on PRP-1 column: (A) Total

ion current of positive ion full scan mz [100-1000]; (B) EIC for 2-oleic

imidazoline mz 307.5 and (C) 2:l-oIeic imidazoline mz 614.7. 5 \iL

injections (50 ^ L sample OI/l in 450 methanol:water:TFA (70:30:0.1

v/v/v)).

101

0.57 100

8

®

I 50 cr

0.61

0 100

50

0

12.43

10 15 Time (min)

NL 8 89E6 TIC

NL; 4 54E5 m/z = 307 0-308 0

13.23 2 43E6

614 2-615 2


isocratic elution with 0.1% TFA in methanol:water (90:10 v/v) on PRP-1

column: (A) Total ion current of positive ion full scan mz [100-1000]; (B)

EIC for 2-oleic imidazoline mz 307.5 and (C) 2:l-oleic imidazoline m/z

614.7. 5 injections (50 fiL sample OI/ l in 450 methanol waterTFA

(70:30:0.1 v/v/v)).

102

100

50

NL: 5 63E7

50

g 100

E I 0 1100

S. 50

0

100

50

0

D

RT: 5 64

RT; 9.50

^

10 Time (min)

TIC

RT: 16.03 NL:

L 206E7 m/z = 614.2-6152

NL: 2.03E6 m/z = 349 9-350 9

NL: 673E5

RT 16 05^7 0.308 0

15 20

Figure 4.9 HPLC/ESI-MS mass chromatograms of 2:l-oleic imidazoline product by

gradient elution [(time/%A) 0/70-1/70-15/100; A) 0.1% TFA in methanol

and B) 0.1% TFA] on PRP-1 column: (A) Total ion current of positive ion

full scan mr [100-1000]; (B) EIC for 2:1-oleic imidazoline m r 614.7, (C)

l:l-oleic imidazoline and (D) 2-oleic imidazoline mz 307.5. 5

injections (50 ^ L sample 01/1 in 450 îL methanol:water:TFA (70:30:0.1

v/v/v)).

103

100 • NL: 1.12E8

50 TIC

8 100 ^^^^ NL

I 3 R 1 ? 5 0 d ^ = E d I \ 614.2-615.2

S . . ^ RT:1.75 :g '00 - 4 ^ NL: ® ^ 2 38E6

5 0 d f- m/z = 349 9-350 9

100 f ^ T s o e / \ D 6 46E5

50 \ ^ = ^ — 0 1" " I " n " " I " " I '

RT: 14.66 A 307 0-308 0

10 15 20 Time (min)


gradient elution [(time/%A) 0/80-1/80-15/100; A) 0.1% TFA in methanol

and B) 0.1% TFA] on PRP-1 column: (A) Total ion current of positive ion

full scan m r [100-1000]; (B) EIC for 2:1-oleic imidazoline m r 614.7, (C)

l:l-oleic imidazoline and (D) 2-oleic imidazoline mz 307.5. 5

injections (50 sample OI/l in 450 nL methanol:water:TFA (70:30:0.1

v/v/v)).

104

Two other chromatographic phases were investigated. MN200 is a novel hyper-crosslinked

polystyrene-divinylbenzene phase that shows strong retention for hydroxybenzenes,

polyphenols (Appended is a report* ^ (Analysis of Highly Polar Low Molecular Weight

Organic Molecules: Part 2 -New Methods for the Identification of Polar Chemicals in

Complex Mixtures) of an investigation carried out on this phase by the present author) and

other ionic or polar compounds ,E lut ion of 2:1/1:1-01 was observed with 0.1% TFA

in methanol. However, 2:1-01 eluted as a very broad peak (k = 4.5-11). A porous graphitic

carbon phase (Hypersil Hypercarb)"^ "^ was also investigated, but no elution of 2:1/1:1-

01 or PI was observed with 0.1% TFA in methanol. No further analysis was carried out

with either phase.

4.3.4 HPLC/ESI-MS analysis of2:l-PI synthesised by Dean and Stark reflux

Having shown that the PRP-1 stationary phase gave good chromatographic separations of

oleic acid based imidazolines, the 2:1-PI synthetic product and the reaction sub-samples

(Section 4.2.5.3) were analysed by HPLC/ESI-MS using gradient elution determined for

2:I-OI. Protonated ions for the main products and intermediates: 2:1-PI {m/z 562.6;

Structure VTIT, R and Ri = C15H31, Figure 3.1), l:l-PI (m/z 324.4; Structure VII, R =

C15H31. Figure 3.1), PI {m/z 281.3; Structure IX, R = C15H31, Figure 3.1), monoamide {m/z

342.4; Structure UI and/or fV, R - C15H3, , Figure 3.1) and diamide (m/z 581.6; Structure V

and/or VI, R and Ri = C15H31, Figure 3.1) could be observed in the TICs obtained. The

retention times (Ri, Table 4.1), and auto-integrated peak areas (AA, Table 4.2), were

determined for each extracted ion mass. The most striking feature comparing TIC and EIC

peak heights, was that the ratio of l:l-PI decreased relative to 2:1-PI from - 1:1 for the 7

hour sample to 1:3 at 71 hours and is clearly seen in the m/z 562.6 and m/z 324.4 E I C

(Figure 4.11) and as a plot of the percentage relative ratios of the auto-integrated peak

areas (AA) (Figure 4.12). This suggests that the reaction proceeds via reaction pathway 2

shown in Figure 4.1, in which a monoamine is initially produced from the fatty acid/DETA

105

salt, followed by cyclisation to 1:1-PI with subsequent condensation at the amine with

fatty acid to 2:1-PI. The mono and diamide precursors are present in only small quantities

relative to there imidazoline products (<10% and <1% respectively; Table 4.3) and

therefore cyclisation must be rapid. The final recrystallised (from acetone) 2:1-PI product

contained 6% 1:1-PI relative to 2:1-PI by peak area and even lower quantities of the

mono/diamides (Table 4.3). Comparison of the retention times for the palmitic and oleic

compounds indicates that they would be resolved by the HPLC method.

Table 4.1 HPLC/ESI-MS retention times for extracted mass chromatograms for

protonated ions of: PI {m/z 281.3), 1:1-PI (m/z 324.4), monoamide (m/z

342.4), 2:1-PI (m/z 562.6), and diamide (m/z 580.6). Conditions as given in

Figure 4.11

2:1-PI Sample

Retention Time (Rt) 2:1-PI Sample / n ^ 281.3 m/z 324.4 m/z 342.4 m/z 562.6 m/z 580.6 Blank 0.51 nd* nd nd nd nd 7hr 0.46 3.37 1.05 2.23 13.36 14.33

23 hr 0.45 3.47 1.07 2.27 13.38 14.43 30 hr 0.46 3.42 1.05 2.25 13.3 14.33 47 hr 0.45 3.38 1.05 2.27 13.37 14.49 71 hr 0.45 3.48 1.08 2.37 13.27 14.32

FP(144hr) 0.43 nd 1.08 2.32 13.36 14.36 compound (to) * Not detected (nd)

Table 4.2 Peak areas for detected peaks given in Table 4.1

2:1-PI Sample

Peak Area (Auto Integrated) 2:1-PI Sample m/^ 281.3 m/z 324.4 m/z 342.4 m/z 562.6 m/z 580.6 Blank nd nd nd nd nd 7hr 1227078 91438661 7092118 113142354 729504

23 hr 1645295 89359329 8096950 162514597 1193184 30 hr 1120770 61585189 4436593 131399597 1137245 47 hr 1202958 55279426 1245089 135720318 646090 71 hr 688960 55560829 868047 156507653 347757

FP (144 hr) nd 9885036 709099 216430843 347237^

106

Table 4.3 Relative percentage peak area ratios of peaks given in Table 4.1

2:1-PI Sample

% Relative ratios of EIC /n/!z Peak Areas 2:1-PI Sample 324.4/562.6 580.6/562.6 324.4/342.4

7hr 80.8 0.6 7.8 23 hr 55.0 0.7 9.1 30 hr 46.9 0.9 7 2 47 hr 40.7 0.5 2 3 71 hr 35.5 0.2 1.6

FP (144 hr) 4 6 1.6 7.2

100

100

RT: 1 05

RT 1.07

I 100 c

^ 100 i RT: 1.08

100

RT: 1.08

m/z = 323 9-324.9+562.1-563.1

RT: 13.36

13 RT: 13.38

NL 4 6 3 E 6

NL: 5 6 8 E 6

RT: 13.30 NL 4 4 9 E 6

RT: 13.37

RT: 13.27

RT: 13.36

5 10 15 Time (min)

20

7 h r

2 3 h r

3 0 h r

N L 4 . 7 0 E 6 4 7

NL 5 3 1 E 6 7 ,

NL: 7 6 3 E 6 Final product

Figure 4.11 HPLC/ESI-MS mass chromatograms of 2:1-palmitic imidazoline synthesis

sub samples by gradient elution [(time/%A) 0/80-1/80-16/100; A) 0.1%

TFA in methanol and B) 0.1% TFA] on PRP-1 column: EIC's for 1:1-PI

and 2:1-PI (m z 325.4 and 562.6) at 7/23/30/47/71 hours and final product.

107

(0

90

80

70

60

50

40

30

20

10

0 10 20 30 40 50

Reaction Time (Hours)

60 70 80

Figure4.12 Plot of the percentage relative peak area ratios of l:l-PI/2:l-PI against

reaction time for solvent reflux reaction of palmitic acid with

diethylenetri amine.

4.3.5 Investigation of the HPLC/ESI-MS limits of detection for 2;7-P/ in full scan and

selected ion monitoring mode

A series of standards (0.0001 to 100 ^g mL'^) of 2:1-PI (Sample Pl/l-fp; Section 4.2.5.3)

were analysed by HPLC/ESI-MS using positive ion, full scan mode {m/z 100-1000) and

selected ion monitoring (SIM) for 1:1-/2:1-PI {m/z 324A, 0-6 min and m/z 562.6, 6-30

min; isolation width m/z 1.5) in order to determine appropriate concentrations for further

evaluations, to obtain an idea of the potential limits of detection and to establish external

calibration responses. Peak retention time (Rt; Automatic peak detection), auto-integrated

peak areas (AA), peak height (AH; Automatic peak height detection) and signal to noise

ratios (S/N; Xcalibur software calculated) from extracted ion and selected ion

chromatograms of the 2:1-PI {m/z 562.6) of each standard are given in Table 4.4. For 2:1-

PI {m/z 562.6) the lowest detectable peak, was obtained for the 0.1 g mL'* standard in

108

both SIM and EIC mode. However, the peak areas for the SIM mode were twice that of the

E I C peaks. The signal to noise ratio of four at the 0.1 \ig mL * level for the E I C (m/z 562.6)

is about the limit of detection (S/N = 3) whilst for the SIM at S/N= 11, is considered to be

about the limit of quantitation (S/N = 10). Plotting the peak areas against concentration

(Figure 4.12), a good linear trend was shown for the SIM and E I C chromatograms (R} =

0.9991(1) and 0.9990(6) respectively) in the concentration range 0.1 to 100 ng mL''. Only

one data set was obtained because the chromatographic and mass spectrometer conditions

were still being evaluated at this point and were subject to constant change; therefore

repeatability tests and statistical analyses could not be conducted. The lowest detected

standard at 0.1 ng mL'* equates to 0.5 ng analyte on column (for the 5 ^ L injection), which

with the eluent split (1/5* to the mass spectrometer) means only 0.1 ng sample is reaching

the mass spectrometer. However, even with this amount the detection limits determined

were lower than previously published for imidazolines (50ng mL * and 150 ^g mL'*).^^'^ It

was determined that 1 - 10 ^g mL"' would be optimum for further evaluation both for

HPLC/ESI-MS and for solid-phase extraction procedural development. As the objective

was the determination of unknown samples and not achievement of the lowest possible

detection limit, selected ion monitoring was not considered necessary for development and

all further analyses were carried out in the full scan mode with a wade mass range (m/z

100-1000 or greater) in order to observe ions from a greater range of compounds.

Table 4.4 Selected ion and extracted ion chromatogram peak data for a series of 2:1-

PI (m/z 562.6) standards; 5^L injections on PRP-1 with gradient [(time/%A)

0/75-0.5/75-15/95; A) 0.1% TFA in methanol and B) 0.1% TFA]

Standard Selected ion m/z 562.6 Extracted ion m/z 562.6 Mg mL'^ AA AH S/N Rt AA AH S/N

100 12.93 2040366555 76589953 314 12.94 1.11E+09 40741369 411 10 13.17 140138626 3829811 126 13.19 75588309 2081006 110 1 13.25 15460647 442662 182 13.28 8330346 236135 103

0.1 13.14 1223257 40123 11 13.17 564874 16937 4 0.01 n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.

109

2 50E+09

2.00E+09

1.50E+09

I , o

OOE+09

5.00E+08

O.OOE+00

R^= 0.99911

• S I M

u g mL ^

Figure 4.13 Plot of the selected (SIM) and extracted (EIC) ion peak area for 2:1-PI (m z

562.6) standards against concentration. Linear trend line and value

shown. Conditions given in Table 4.4.

Following the promising results of the above calibration, a second calibration series of

standards (0.0124 to 12.4 ^g mL"') of 2:1-PI (Sample Pl/l-fp; Section 4.2.5.3) was earned

out in full scan mode {m z 100 - 1000) with an increase in injection volume (5 to 20 ^L) , a

small change in gradient (to 95% A in 11 minutes compared to 15minutes previously) and

half magnitude dilutions at the 0.0620 and 0.620 ^g mL'' level. Extracted ion

chromatogram (m z 562.60) peak data for 2:1-PI, are given in Table 4.5. An order of

magnitude improvement in detection was observed, with a peak at a signal to noise ratio of

three, for the 0.0124 ^g mL'' standard. A plot of the peak areas against concentration

(Figure 4.14) show a very good order two polynomial trend (R^ = 1.0000) compared to the

previous linear calibration (Figure 4.13). However, when the previous calibration was re

examined and an order two polynomial trend line fitted (Figure 4.15), an R^ = 1.0000 was

110

also observed, except with an opposite slope (increasing slope with increasing

concentration). The reason for these differences was not clear and required further

investigation once an optimised system had been determined.

Table4.5 Extracted ion chromatogram peak data for a series of 2:1-PI (mz 562.6)

standards; 20nL injections on PRP-1 with gradient [(time/%A) 0/75-0.5/75-

11/95; A) 0.1% TFA in methanol and B) 0.1% TFA]

Standard Extracted ion m/z 562.6 Rt AA AH SN

12.4 12.65 366931542 11493193 124 1.24 12.68 59875892 1946530 96 0.620 12.74 32735977 1113637 44 0.124 12.78 5693611 248173 14 0.0620 12.74 3777264 140890 9 0.0124 12.81 792544 48515 3 Blank n.d. n.d. n.d. n.d.

4 006+08

3 506*08

3 006*08

S 2 506*08

I 2 006 *08

I 1 506*08

1.006*08

5 006*07 J

0 006*00^

y = -1706094 7x^ * 50717601 9x * 358790 8 R2 = 1 0000

6 8 1C 12 ' 4

Figure 4.14 Plot of the extracted (EIC) ion peak area for 2:1-P1 standards (mz 562.6)

against concentration. Order two polynomial trend line, equation and R"

value shown. Conditions given in Table 4.5.

I l l

2 506+09 • SIM

XEIC

y = 71845 • 13209269 1x + 981194.8 « R2= 1 0000 S

1 506+09 ^ I y = 402781x2 + 7115051 8x + 479530 1

R2= 1 0000

< 1 006+09 ^ -X.

C

5 006+08

0 O C E * X

Figure 4.15 Plot of the selected (SIM) and extracted (EIC) ion peak area for 2:1-PI

standards (mz 562.6) against concentration. Order two polynomial trend

line, equation and R' value shown (c/Figure 4.13). Conditions given in

Table 4.4.

4.3.6 Investigation of ion-pair and solvent systems for the HPLC/ESI-MS detection

l:1-Pland 2:1-PI

It is widely known that TFA can cause signal suppression of analytes during electrospray

ionisation.'^^'*^' Therefore, heptafluorobutyric acid (HFBA) was investigated as a possible

alternative ion pairing agent. HFBA generally provides greater retention due to the longer

per-fluoro chain, but can have less ESI suppression. 0.1% TFA was replaced with

0.1% HFBA in both mobile phases (A; methanol and B; water) and the 23 hour 2:1-PI

synthesis sub-sample analysed (Sample PI/l-23hr; Section 4.2.4.3). The Pl/l-23hr sample

was ideal for investigating the chromatographic conditions as it contained approximately

equal quantities of both 1:1-PI and 2:1-PI. HFBA had a detrimental effect on the elution of

1:1-PI and caused ^fronting' of the peak (Figure 4.15). It was also observed that the

112

background was generally noisier than spectra obtained with TFA as the agent (spectra not

showTi) and therefore HFBA was not further evaluated.

100

80

60

40 < I 100

80

60

40

20

RT: 2 96

RT: 13.06

— •— '' '"^^ - 10 15

Time (min)

NL: 734E7 TIC

A

NL: 2 14E7 m/z = 323 9-3249> 562 1-563 1

20

Figure 4.16 HPLC/ESI-MS mass chromatograms of 2:1-palmitic imidazoline synthesis

23hr sub sample by gradient elution with heptafluorobutyric acid ion-pair

reagent [(time/%A) 0/80-1/80-16/100; A) 0.1% HFBA in methanol and B)

0.1% HFBA] on PRP-1 column: (A) total ion current chromatogram and (B)

EIC's for 1:1-PI and 2:1-PI {m z 325.4 and 562.6).

The organic/water content of eluent is also known to affect electrospray ionisation

efficiency. Both 100% water and 100% organic are detrimental. Generally 50% to 80%

organic phase is optimal for LC/ESl-MS of many compounds. For elutions carried out so

113

far, the gradients have started at 75% organic content (methanol) and finished with 95 or

100% organic. The 2:1-imidazoline compounds do not elute until the organic content is

about 95%. Ethanol as the organic eluent was evaluated to see if the 2:1-imidazoline

compounds could be eluted with a higher aqueous content. A gradient elution (60 - 100%

in 15 minutes of 0.1% TFA in ethanol) of PI/l-23hr sample (Figure 4.17) showed that 2:1-

PI eluted in 10.49 minutes and - 80%, 0.1% TFA in ethanol with a good peak shape. 1:1-

PI eluted in 1.71 minutes with a symmetrical peak and sharper than observed in previous

methanol elutions. The improvement in tailing of the 2:1-PI peak was due to a 0.1 minute

delay in the start of the gradient rather than the 0.5 minute delay used previously. The

initially 0.5 minute delay was set in order to allow increased retention (relative to the

solvent front) of the 1:1-PI and also the requirement of the P580 binary pump to have a

time set after to for the start of a gradient profile. 0.1% TFA in both methanol and ethanol

are suitable for elution of 1:1-PI and 2:1-PI and required further evaluation with other

imidazoline compounds. Acetonitrile (MeCN), which is also a common reverse-phase

eluent, was not evaluated as neither the synthesised compounds nor the commercial

imidazoline products were soluble in MeCN.

114

^ 80

1 51E8

RT: 1.71

RT: 10.49

1 37E7 nVz =

323 9-324 9> 562.1-563 1

B

5 1 1 11 M I 1 . - r . | . . r r j . . . . i . M n i . M f

10 Time (min)

15 20

Figure 4.17 HPLC/ESI-MS mass chromatograms of 2:l-palmitic imidazoline synthesis

23hr sub sample by gradient elution with ethanol [(time/%A) 0/60-0.1/60-

15/100; A) 0.1% TFA in ethanol and B) 0.1% TFA] on PRP-1 column: (A)

total ion current chromatogram and (B) EIC's for 1:1-PI and 2:1-PI (m z

325 A and 562.6).

115

4.3.7 Synthesis of l:l-oleic imidazoline by Dean and Stark reflux in xylene

The 23 hour sub-sample from the 2:1-PI synthesis was useful for developing the

HPLC/ESI-MS due to the presence of both the 1:1 and 2:1-PI compounds. However, in

order to quantitate the relative responses, pure individual compounds were required. The

1 :l-imidazoline is predicted to be the major product if DETA and fatty acid are allowed to

react in a 1:1 molar ratio' *' ''*' ' - '" although only Bondareva ei. al^^ isolated and

characterised the monoamine intermediate and l:l-imidazoline product. A 1:1 molar ratio

of DETA and oleic acid were reacted by Dean and Stark reflux in xylene for 91 hours

(Section 4.2.5.4). Sub samples of the reaction solution, were taken at 1,3,19 and 91 hours.

HPLC/ESI-MS analysis of each sample was carried out. In the 1 hour sample, ions could

be identified in the mass spectra and extracted for the 1:1-01 (rn/z 350.4; peak 1; 100%),

monoamide {m/z 368.3; peak 2; 30%), 2:1-01 (/n/z 614.7; peak 3; 80%) and the diamide

{m/z 632.6; peak 4; 10%) (Figures 4.18 and 4.19). 1:1-01 is the main product (100%

relative abundance in extracted ion chromatogram; Figure 4.18) whilst the 2:l-OI product

is present at 60% relative abundance. This was not expected for such a short reaction time,

as an excess of fatty acid, higher temperature or longer reaction times are generally

required for production of 2:l-imida2olines.' ' ^ '^'^ Over the course of the reaction (Figure

4.20), it can be seen that the monoamide (m/z 368.3; peak 2) decreased from 30% to 3%,

whilst the 2:1-01 {m/z 614.7; peak 3) decreased from 80% to 46%. This suggests that there

was little change in the amount of 2:1-01 produced af er 1 hour and that the relative

abundance change was due to condensation of the monoamide to the 1:1-01 product. It

could also be seen that the diamide product was present at 1 hour and decreased from 10%

to <1% throughout the reaction {m/z 632.6; peak 4; (Figures 4.18 and 4.20). This means

that both the monoamide and diamide were formed before cyclisation to the respective

imidazoline and that both reaction pathways 1 and 2 (Figure 4.1) are possible. The

reactions carried out so far, thus highlight why the literature has reported conflicting results

and disagreements on the reaction mechanisms and pathways. It was also becoming

116

apparent from the above studies that there were several potential remaining problems for

the method. For example, the presence of fatty acid, fatty acid amine or amide salts could

not be detected by the HPLC/ESI-MS system; hydrolysis of the imidazolines during

sample preparation might occur (during or before HPLC/ESI-MS); the oleic imidazolines

were oils and recrystallisation was not possible thus a method of purification was required.

RT: 3.26

8 c ro "D C

(D

ro ID

100

90

80

70

60

50

40

30

20

10

1 m/z 350.4

2/n/2 368.4

RT: 4.96

5 10

3/n/z614.7

RT: 15.20

NL: 6.33E6 m/z = 349.9-350.9+ 367.9-368.9+ 614.2-615.2+ 632.2-633.2

4 w/z 632.7

RT: 16.32

15 20 Time (min)

Figure 4.18 HPLC/ESI-MS extracted mass chromatogram of; 1:1-01 {m/z 350.4; peak

1), monoamide {m/z 368.3; peak 2), 2:1-01 {m/z 614.7; peak 3) and the

diamide {m/z 632.6; peak 4) for I:l-oleic imidazoline synthesis Ihr sub

sample, by gradient elution with ethanol [(time/%A) 0/55-0.1/55-20/100; A)

0.1% TFA in ethanol and B) 0.1% TFA] on PRP-1 column.

117

100-1

50

350.4 38.5

260.9 583.7 733.6 920.5

, l . : v , i i - . . , . i i , | . . i l | . . n

8

11 l | i o o ^ a: <

50-1

500

614.7

1000

38.6

260.9

4 612.7.

616.7 855.6

500 m/z

1000

100^

50

38.6

368.3

597.8 733.6 920.6 | i | i l V | i i i ' . | i i L . | i ' f . . ' ) l i . i | i ' i . . | i i . i | i i n |

500 1000

100

50 i

38.7

260.9 274.9 632.6

453.8

-TT-n-TTTTTTT

633.7 855.7 J|J,,ii|H<,t,Jito|iUi,î,

500 m/z

1000

Figure 4.19 Mass spectra of peaks 1-4 shown in Figure 4.18.

118

0

Peakl m/z 350.4

Peak 2 m/z 368.4

Time (min)

Peak 3 m/z 614.7

Peak 4 m/z 632J

I h r

19 hr 91 hr

20

Figure 4.20 HPLC/ESI-MS extracted mass chromatograms of 1, 3, 19 and 91hr sub

samples for l:l-oleic imidazoline synthesis. Peaks 1-4 and conditions given

in Figure 4.18.

119

4.3,8 Synthesis of 2:]-oleic imidazoline by Dean and Stark reflux in xylene and

purification by vacuum distillation

Bondareva et. al.^^ used vacuum distillation to isolate monoamine, l:l-imidazoline and

2:1-imidazoline produced by sequential time/temperature stages by solid-phase reaction of

DETA with 2-ethylhexanoic acid. In the present study, in an attempt to determine a

distillation procedure, a larger scale (100 g oleic acid) Dean and Stark reflux synthesis of

2:1 -01 was carried out over 95 hours with sub samples taken at 5, 23 and 95 hours (Section

4.2.5.5). HPLC/ESI-MS analysis of each sample was carried out and for each sample, ions

could be identified and extracted for the I: I -01 {m/z 350.4; peak 1, monoamide {m/z 368.3;

peak 2), 2:1-01 {m/z 614.7, peak 3) and the diamide {m/z 632.6; peak 4) (Figure 4.21)

products. 2:1-01 was the main product (100% relative abundance in extracted ion

chromatograms; Figure 4.21) whilst the 1:1-01 product decreased as the reaction

progressed and was present at 55, 38 and 28% relative abundance at 5, 23 and 95 hours

respectively. An increase in the diamide is observed in the 23 hour EIC (Peak 4; Figure

4.21); however, this is due to hydrolysis of the 2:1-01 during the rotary evaporation of

xylene. This highlights the potential and ease of hydrolysis of the 2:1-01. This was further

confirmed when an attempt to vacuum distil a quantity (64 g) of the 2:1-01 final product

(Section 4.2.5.6) resulted in the formation of a white solid fi-om what was initially a

yellow vapour which condensed to a yellow oil. An air leak could clearly be seen but

proved difficult to seal. A further vacuum distillation was not carried out as the remaining

2:1-01 product was used for solid-phase extraction experiments (Chapter 3). Over 12

weeks storage at 4 ^C in a stoppered and sealed round bottom flask (except for removal of

aliquots), a crystalline white precipitate appeared and gradually increased in amount over

time. The contents of the flask were filtered under vacuum with a washing of hexane. The

collected precipitate was washed with hexane and dried at 40* C for 24 hours. HPLC/ESI-

MS analysis of the collected solids, showed that the major peak in the extracted

chromatogram (Peak 2, m/z 632.7; Figure 4.22 and 4.23) corresponded to the expected

120

mass for protonated oleic-diamides. Indeed. MS" analysis (Appended; Figures A2 - A6)

was consistent with identification of the product as oleic-diamides and *H nuclear magnetic

resonance spectroscopy (Appended; Figure A7) was consistent with the product being 1,3-

oleic diamide (Structure V, Figure 3.1) as discussed in Chapter 5 (section 5.3.3.3 and

5.3.3.4). A small amount of 2:1-01 was also present (Peak 1, m/z 614.7; Figure 4.22 and

4.23).

e

<

cs

0

Peakl m/z 350.4

Peak 2 m/z 368.3

Time (min)

Peak 3 m/z 614.7

Peak 4 m/z 632.6

5hr

95 hr

20

Figure 4.21 HPLC/ESI-MS extracted mass chromatograms of 1:1-01 {m/z 350.4; peak

1), monoamide {m/z 368.3; peak 2), 2:1-01 {m/z 614.7; peak 3) and the

diamide {m/z 632.6; peak 4) for 5, 23 and 95hr sub samples of 2:1-oleic

imidazoline synthesis. Gradient elution with ethanol [(time/%A) 0/55-

0.1/55-20/100; A) 0.1% TFA in ethanol and B) 0.1% TFA] on PRP-1

column.

121

100

90

80

70

60

50

40

30

20

10

0

16.52

Peak! ^ m/z 632.6

Peakl m/z 614.7

15.84

0.48 J

NL: 4.70E6 m/z = 349.9-350.9+ 367.9-368.9+ 614.2-615.2+ 632.2-633.2

17.34

5 10 15 20 Time (min)

Figure 4.22 HPLC/ESI-MS extracted mass chromatogram of; 1:1-01 (m/z 350.4; no

peak ), monoamide {m/z 368.3; no peak), 2:1-01 {m/z 614,7; peak 1) and the

diamide {m/z 632.6; peak 2) for oleic diamide. Gradient elution with

methanol [(time/%A) 0/75-0.1/75-17/100; A) 0.1% TFA in methanol and B)

0.1% TFA] on PRP-1 column.

8

c

c

o >

(D

100

50 i

614.7

430.9

423.0

Peakl

6.15.7

838.6 I

500 m/z

1000

100^

50 i

632.7

308.5 430.9

Peak 2

633.7

792.6 838.6 500

m/z

I I : J 1 I I 1 I I I 1000

Figure 4.23 Mass spectra of peaks 1 and 2 Figure 4.22.

122

4.3.9 Investigation of the HPLC/ESI-MS response for 2:1-01

A series of 2:1-01 standards (0.005 - 10 ^g mL**; Section 4.2.5.5) was analysed to

determine the response by HPLC/ESI-MS in order to determine the best method for

evaluating and providing an external calibration method for both 2:1-01 and 2:1-PI. Peak

retention time, integrated area and signal to noise ratio for the protonated 2:1-01 ion {m/z

614.7) are given in Table 4.6. The lowest detectable peak was at the 0.005 ng mL"'

concentration (S/N = 3) with the 0.01 ig mL * standard giving a signal to noise ratio of

four. The 0.01 - 10 ng mL'' standards were re-analysed the following day (data in Table

4.6). The Xcalibur software-determined signal to noise levels show that the background

signal response was highly variable for the eluent system with the signal to noise ratios

increasing to maximum values for the l^g mL * concentrations (S/N = 480 and 218, day 1

and 2 respectively; Table 4.6) and decreasing at the higher concentrations. Plotting the m/z

614.7 peak area response against concentration for the day 1 and 2 standards (0.01 - 10 ng

mL"'; Figure 4.24) a curvilinear response was observed. The relative response decreased

above 1 jig mL"'. This decrease in response at higher concentrations is normal for the

electrospray ionisation process and is dependent on the ease of ionisation of the compound

and the total concentration of ions in the eluent system. The response is linear for both day

one and day two analyses in the range (0.01 - 1 ^g mL"'; Figure 4.25 and 4.26

respectively) with values of 0.9900 and 0.9777 respectively. There was greater variation

observed in the day to day response of the 0.5 and 1 ng mL*' samples (Figure 4.25 and

4.26 respectively). However, when the day one and day two responses were averaged

(Figure 4.27) a very good linear trend (R^ = 0.9997) was observed. Solvent blanks were

examined by LC/ESI-MS between each standard and show that sample carryover was

present only in the inter-sample blanks from the 1 jig mL'' concentration and higher (Table

4.6). This indicates that sample carryover due to the system should not be a problem in the

linear response concentration range. The calibrations carried out showed that an external

123

calibration method for 2:1-01 could be developed, although a more detailed study would

be needed to be carried out on sample repeatability and day to day variability of response.

Table 4.6 Extracted ion chromatogram peak data for a series of 2:1-01 {m/z 614.7)

standards; 20nL injections on PRP-1 with gradient elution [(time/%A) 0/75-

0.1/75-17/100; A) 0.1% TFA in methanol and B) 0.1% TFA]

Standard Day 1 Day 2 Rt AA SN Rt AA SN

Blank n.d 0.001 n.d Not run 0.005 15.77 274417 3 Not run Blank n.d n.d 0.01 15.88 483151 4 15.91 607910 6

Blank n.d n.d 0.05 15.69 3644524 32 1617 3944367 23

Blank n.d n.d 0.1 15.66 8136643 79 1608 8099689 37

Blank n.d n.d 0.5 15.61 32884677 208 16.13 40737031 163

Blank n.d 76.05 309755 3 1.0 15.61 81621473 480 16.11 62187936 218

Blank 15.67 534463 5 15.92 679758 5 5.0 15.64 202699140 168 15.95 193559699 107

Blank 15.74 2760026 20 16.02 3105846 23 10 15.63 352526470 90 15.95 354972761 98

124

4 00&K)8

3.50E+08

300EK)8

? 2.50EK)8

N E

< s Q.

2.00E+08

1.50E+08

1.00E+08

5.00E+07

1^

• Day 1 xDay 2

• X

OOOE OO 10 12

mL-

Figure 4.24 Mass spectral ion current response {m r 614.7) of 2:l-OI standard

solutions (0.01 - 10 ^g mL'') on consecutive days.

9.00E+07

8.00B-07

7 OOE+07

• 6.00E+07

5,00E+07

£ 4.00&-07

2 3.(X)E+07 Q.

2.00E^07

1 OOE+07

0.00 E*00

R 2 = 0.9900

0.2 0.4 0.6 0.8 1.2

[iQ mL ^

Figure 4.25 Mass spectral ion current response (/n r 614.7) of 2:1-01 standard solutions

(0.01 - 1 îgmL 'Vnday 1.

125

7 00E*07

6 OOE+07

5 00E*07

07 5 4 00E-^

fT3 O < 3 00E-^07

Q. 2 00E+07

1 OOE-^07

0 OOEÔO ^

0 2 0.4 0 6

= 0.9777

0 8 1 2

Figure 4.26 Mass spectral ion current response {mz 614.7) of 2:l-OI standard solutions

(0.01 - 1 ^gmL' ' )onday 2.

800E+07

7 OOE+07

6 00E*07

«0 5.00E*07

FT = 0.9997 15 400E-^07

3 0 C E - C 7

2.00E+07

1 OOE-^07

0 OOE+OO

1.2

Figure 4.27 Averaged (day 1 and 2) mass spectral ion current response (w r 614.7) of

2:1-01 standard solutions (0.01 - 1 mL"').

126

4.3.10 HPLC/ESI'MS amilysis of a commercial imidazoUne-based corrosion inhibitor

Having shown that synthetic palmitic and oleic acid-derived imidazolines and amides

could be separated, the HPLC/ESI-MS method was applied to a commercial imidazoline

corrosion inhibitor product (CI-El) . The total ion chromatogram (Figure 4.28A) revealed a

series of small broad peaks in the first five minutes and a large broad peak at about sixteen

minutes, which showed enhanced resolution and intensity in the extracted base peak

chromatogram (Figure 4.28B). Extracting selected ion chromatograms of m/z values

observed in the meiss spectra under the peaks and observed in a previous infusion ESI-MS

analysis (See Chapter 3 section 3.3.2) of the product, the presence of a range 1:1- and 2:1-

imidazolines (Figure 4.29) and the corresponding monoamides and diamides (Figure 4.30)

derived from Cig acids with up to three degrees of unsaturation (Cig.o, Ci8;i, Cig:2 and

Ci8:3)and 1:1- and 2:1-Imidazolines (Figure 4.31) derived from C20 acids with up to three

degrees of unsaturation (C20:o, Cio i, C20:2 and C20:3) was observed. The extracted masses

correlated with those observed in the infusion ESI-MS spectra of the product and some

separation of the various structiu-al isomers (Chapter 3, section 3.3.2) was observed (Figure

4.29, 4.30 and 4.31). The resolution was poor for most of the isomers and needed to be

enhanced to near baseline resolution to enable MS° analysis. The optimised method may

allow 'fingerprinting' of commercial products and their detection in environmental and

other samples.

127

glOO,

_

® _> ®

_>

| 4 0 t a:

0.48 1

20 z JU

15.83 NL: 2.28E7 TIC

25

100 t ]

15.67

15.88 14.94

16.22 i so-

14.60

14.15

NL: 3.44E6 Base Peak m/z = 100.0-1000.0

10 15 20 Time (min)

Figure 4.28 HPLC/ESI-MS mass chromatograms of imidazoline corrosion inhibitor

product (CI-El); (A) total ion current chromatogram and (B) base jDeak

chromatogram. Gradient elution with methanol [(time/%A) 0/75-0.1/75-

17/100; A) 0.1% TFA in methanol and B) 0.1% TFA] on PRP-1 column.

128

100

50

8 100

I 50 c n

1100 I 50

1 I

2.11

3 18

2.86

100 4.20

50 2.77

NL 518E5 m/z = 346 0-347 0

NL: 1.63E6 m/:r = 348 0-349 0

NL: 1.40E6 m/z = 350 0-351 0

NL: 1.42E5 m/z = 352 0-353 0

0 5 10 Time (min)

B

100 50

14 94 NL: 1 94E6 m/z = 608 2-609 2

'15.38

15.27 N L : 3 ^ E 6 AT m/z =610 2-6 1588

100

50 15.63

15 67 NL 3 00E6 16 3 1 ^ =612 2-613.2

15 01 NL:1.16E6 m/z =614.2-615.2

10 15 20 Time (min)

Figure 4.29 HPLC/ESI-MS extracted mass chromatograms of imidazoline corrosion

inhibitor product (CI-El); (A) Cign l:l-imidazolines and (B) Ci8„/Ci8:„ 2:1-

imidazolines. Conditions as Figure 4.28.

129

B

100

50

3.52

4.49

§ 100 • D C

I 0

4.27

5.15 u.oo

.'

I 100

^ 50

5.31

1.10

100

50

7.44

NL; 2.25E5 ^ = 364 0-365 0

NL: 5 75E5 m/z = 366 0-367.0

NL: 5.15E5 m/z = 368 0-369 0

NL: 2 02E4 m/z = 370 0-371.0

0 5 Time (min)

10

100

50 12.08

15 95 NL 3 67E5 m/z= 626 2-627 2

100

50

100

50

16 18 NL 4 66E5 m/z = 628.2-629 2

12.48

14.15 16.44

100

50

14.60

NL 7 69E5 m/z =630 2-631.2

NL; 1.27E6 m/z =632.2-633.2

10 15 20 Time (min)


inhibitor product (CI-El); (A) C i 8 n monoamides and (B) C i 8 n / C i 8 n

diamides. Conditions as Figure 4.28.

130

A

100

50

710 NL;3.17E5 m/2 = 380 0-381 0

5.05

100

50

5 24 NL: 2 94E5 m/z = 378 0-379 0

4.13

100

50

0

100

50

4.08

3.18

NL: 3 57E5 m/z = 376 0-377.0

NL: 8.40E5 m/z = 374 0-375.0

I ^ ^ 0 5 10

Time (min)

B 18.24

18.07

17.69

17.09

NL: 1 40E5 m/z =672 2-673 2

NL: 2 11E5 m/i =670.2-671 2

NL 2 66E5 m/z = 668 2-669 2

NL 2 06E5 m/z = 666 2-667 2

Time (min)


inhibitor product (CI-El); (A) Czon 1:1-imidazolines and(B) Cio JCion 2:1-

imidazolines. Conditions as Figure 4.28.

4.4 Conclusion

A HPLC/ESI-MS method for the separation and detection of palmitic and oleic acid-

derived 2.1-imidazolines, l:l-imidazoIines, monoamide and diamide compounds was

developed and the ESI-MS responses investigated. The method was used to separate the

imidazoline and amide components of a commercial imidazoline product and separation of

structural isomers was shown. A simple synthesis and purification method of the

compounds was not identified, consistent with confusing literature reports. 74-79.90-100 and

therefore pure compounds could not be obtained for investigation of the relative responses

for the individual compounds. However, the HPLC/ESI-MS method proved to be a

powerful method for monitoring the progress of synthesis and the intermediate compounds

and highlighted some reasons for the contradictory results in the published literature

131

CHAPTER FIVE

Investigation of the thermal synthesis of palmitic acid with

diethylenetriamine (DETA)

This chapter describes the investigation of the reaction intermediates and pathways of solid

phase and xylene solvent-based thermal reactions of fatty acids with diethylenetriamine

(DETA). The reaction products were studied by high performance liquid chromatography

(HPLC) with electrospray ionisation mass spectrometry (ESI-MS) detection. Structural

characterisation was based on electrospray ionisation multistage mass spectrometry (ESI-

MS"), Fourier transform infra red (FT-IR) and ' H nuclear magnetic resonance (NMR)

spectroscopy.

132

5.1 Introduction

Ever since the initial synthesis of Mmidazolines' described by Hofmann* * in 1888, there

has been debate concerning the mechanism of the reaction between fatty acids and

triamines.'^'^^ Indeed, even the existence of the imidazoline compounds in corrosion

inhibitor products has been questioned.^ Yet the subject is of major importance for

synthesis of pure amides and imidazolines and for the efficient deployment of anti-

corrosion measures since the composition of the synthetic mixtures controls their self

assembly as monolayers on metal surfaces and hence their efficency.'^^

Much of the confusion may have arisen from the existence of different mechanisms in the

solid-phase and solvent-based reactions. ^ However, attempts to elucidate the mechanisms

have also been hampered by the lack of sensitive, specific methods for identification of the

reactants, intermediates and products in the complex mixtures resulting from such

reactions. Thus, even recent studies*^ have required isolation and recrystallisation of the

chemicals at each stage, followed by spectroscopic examination by nuclear magnetic

resonance spectroscopy (NMR) and other techniques. Powerful though these methods are,

they are not sensitive to (perhaps important) minor products and intermediates, most of

which are in any case, removed by recrystallisation procedures. This may have led to some

of the misleading conclusions concerning the mechanisms.

The following study was carried out to determine an efficient method for the synthesis of

2:1-palmitic imidazoline. The presence of palmitic-monoamides, palmitic-diamides and

l:l-palmitic imidazoline in reaction sub samples and crude products also allowed an

investigation of the reaction mechanisms to be undertaken.

133

5.2 Experimental

5.2.1 Chemicals

The chemicals used were as described in Chapter 4 (Section 4.2.1).

5.2.2 High performance liquid chromatograpliy with eiectrospray ionisation mass

spectrometry (HPLC/ESI-MS) and eiectrospray ionisation multistage mass

spectrometry (ESI-MST)

HPLC/ESI-MS analyses were carried out with the equipment described in Chapter 4

(Section 4.2.2 and 4.2.3) on a poly(styrene-divinylbenzene) reverse phase column (PRP-1;

50 X 4.1 mm, 5 n, Hamilton, Reno, NA, USA). Sample injections (20 ^L) were made by an

ASI 100 auto-sampler. Gradient elution (Table 5.1) was made with the following eluents:

A) 0.1% TFA in water and B) 0.1% TFA methanol. ESI-MS" analyses were carried out

with the equipment and as described in Chapter 4 (Section 4.2.2).

Table 5.1 Gradient elution profile for HPLC/ESI-MS analysis of imidazoline

syntheses. Eluents; A) 0.1% TFA in water and B) 0.1% TFA methanol

Time (min) 0 0.1 17 27 28 35 % A 25 25 0 0 25 25 % B 75 75 100 100 75 75

5.2.3 Fourier transform infrared (FT-IR) and ' f f nuclear magnetic resonance (NMR)

spectroscopy

FT-IR and ^H NMR spectroscopy were carried out as described in Chapter 4 (Section 4.2.4)

134

5.2.4 Thermal reaction of palmitic acid witit diethylenetriamine in xylene solvent

A thermal reaction of palmitic acid with DETA was carried out in xylene solvent with

removal of water by way of a Dean and Stark apparatus, using the procedure described by

Wu and Herrington^, the only change being that the reaction was conducted at half scale.

Palmitic acid (2.5 g, 9.7 m mole) dissolved in xylene (25 mL) was added, dropwise. over 1

hour, to a solution of DETA (0.98 mL, 9.1 m mole) in xylene (12.5 mL) under reflux. The

reaction mixture was refluxed (4 hr). After cooling a white precipitate was collected by

filtration. The collected solids were recrystallised from ethyl acetate to give a 2:l-palmitic

imidazoline product (1.80 g), m,p. 95 °C with a wax like softening below the liquid point

at 95 °C (///. 85 - 87 ''C for the palmitic acid complex^ ). A sub sample of the crude

reaction mixture was collected before filtration, and xylene removed by N 2 blow down.

The crude and recrystallised 2:1-PI products were prepared for HPLC/ESI-MS from a 1

mg mL * standard (1000 | iL methanol added to 0.0010 g) and diluted to 5 ^g mL"' (5 ^ L of

1 mg mL'' standard added to 995 | iL methanol).

5.2.5 Thermal reaction of palmitic acid with diethylenetriamine without solvent

A thermal reaction of palmitic acid with DETA without solvent was carried out using the

procedure described by Wu and Herrington.®^ DETA (10.32 g, 100 m mole) was heated to

150**C and palmitic acid (51.29 g, 200 m mole) was added in small portions over 2 hours.

The reaction was continued for 5 hours with stirring and maintaining the temperature at

150**C. A sample of the crude cooled, hard waxy product was retained, whilst the

remainder was recrystallised from acetone:toluene (1:1) to give 1,3- palmitic-diamide, m.p.

118°C(//7. m.p. 117- 119**C^^ I16-118*»C'^).

1,3-Palmitic-diamide (5.00 g) was heated to 235°C under reduced pressure (30 mm Hg) for

2 hours {ca 0.5 hr ; Wu and Herrington). The residue was recrystallised from hexane (100

mL) to give a 2:1 palmitic imidazoline product (4.32 g), m.p. 80 °C {lit. 80 - 82 °C^ ; 78 -

135

79 **C'*). The crude and recrystallised diamide products were prepared for HPLC/ESI-MS

from a I mg mL* standard (0.0100 g made up to 10 mL

cyclohexane:melhanol:trichloromethane (4:3:3 v/v/v)) and diluted to 5 ig mL"' (5 of 1

mg mL * standard added to 995 ^ L methanol). The 2:1-PI product was prepared similarly

except the 1 mg mL'' standard was made up with methanol (1000 | iL methanol added to

1.0 mg).


Having carried out a synthesis of 1 :l-oleic imidazoline (Chapter 4; Section 4.3.7) in which

the 1:1-01 was in greater abundance (by HPLC/ESI-MS analysis) relative to the 2:1-01 in

the final crude product and 1:1-PI was observed in sub samples and products of 2:1-PI

syntheses (Chapter 4), it was intriguing to discover, that Wu and Herrington®^ did not

encounter the l:l-imidazolines or monoamides in their study of the thermal reactions of

fatty acids (palmitic and decanoic acids) with diethylenetriamine, even when reacted in 1:1

molar ratios. Although the present author was not aware of the work of Wu and

Herrington^^ at the time the syntheses carried out in Chapter 4 were conducted, the

methods employed by Wu and Herrington were nonetheless similar to those employed

herein, in that reactions were carried out in xylene solvent and by solid phase reaction.

However, there were also some significant differences between them:

• In the xylene solvent method (Wu and Herrington^ ), a dilute solution (0.02

mol) of fatty acid in xylene was added drop wise by syringe over 1 hour to

a refluxing solution of 0.2 mol DETA in xylene with reflux continued for a

further four hours to complete the reaction. A 2:l-imidazoline-fatty acid

complex was isolated by recrystallisation. The method used herein,

136

employed addition of DETA (undiluted) over ca 10 minutes, to a non

boiling solution of fatty acid in xylene and then refluxed for up to 95 hours.

o For the solid phase synthesis (Wu and Herrington ^ \ fatty acid (0.2mol)

was added in small portions over 2 hours to DETA (0.1 mol) heated to 150

**C. The reaction mixture was maintained at 150 **C with stirring for a further

5 hours after which the palmitic-1,3-diamide intermediate was recovered by

recrystallisation. The purified 1,3-diamide was then heated under reduced

pressure (240 **C; 30 mm Hg) for 0.5 hour and 2:1-imidazoline recovered by

recrystallisation. The methods used by the present author employed addition

of DETA over ca 10 minutes to heated (melted) fatty acid. The diamide

intermediate was not isolated.

Wu and Herrington®^ characterised the recrystallised products by Fourier transform

infrared (FTIR) spectroscopy, ' H nuclear magnetic resonance (NMR) spectroscopy, mass

spectrometry (MS), normal phase high performance chromatography (NP-HPLC) and

Schiff base-forming reactions monitored at 410 nm by ultraviolet/visible (LTV/vis) diode-

array spectrophotometer.

The methods described by Wu and Herrington^^ appeared to offer a simple and efficient

route to high yields of a 2:1-palmitic imidazoline-palmitic acid complex (76 %) with

xylene solvent and 1,3-diamide (62 %) and 2:1-palmitic imidazoline (94 %) by solid phase

syntheses. The xylene solvent and solid phase thermal reactions of palmitic acid v th

DETA were therefore carried out as described by Wu and Hem'ngton, ^ to prepare

palmitic-diamide and 2:1-PI for subsequent HPLC/ESI-MS monitoring of oilfield

corrosion products and environmental samples {cf McCormack et. al.^^).

137

5.3.1 Thermal reaction of palmitic acid with dietliylenetriamine in xylene solvent

A thermal reaction of palmitic acid with diethylenetriamine in xylene solvent was carried

out by the method described by Wu and Herrington^^ (Section 5.2.4). A sample of the

crude reaction mixture was collected and the xylene removed with a stream of nitrogen in

order that both the crude reaction products as well as the recrystallised final product could

be studied. HPLC/ESI-MS analyses of both crude and recrystallised products were carried

out and two peaks were clearly seen in each of the total ion (TIC) and base peak

chromatograms (BP) (Figures 5.1 and 5.2). However, the first peak in the crude product

(Figure 5.1; 1.8 min) eluted ca 2.5 minutes before the first peak in the recrystallised

product (Figure 5.2; 4.4 min). Examination of the mass spectra of each component and

mass chromatography (Figures 5.3 and 5.4) of ions typical of l:l-PI {m/z 324.4),

monoamide {m/z 342.4), 2:1-PI {m/z 562.6) and the diamide {m/z 580.6) allowed the

separate products to be identified. Calculation of signal to noise (S/N) ratios and peak areas

allowed estimation of the relative proportions of each component in the crude and

recrystallised products (Table 5.2).

Table 5.1 HPLC/ESI-MS peak retention times (RO, signal to noise ratios (S/N) and

peak area data acquired fi-om the extracted mass chromatograms for

protonated ions of: 1:1-PI {m/z 324.4), monoamide {m/z 342.4), 2:1 -PI {m/z

562.6), and diamide {m/z 580.6) for the crude and recrystallised products of

xylene solvent synthesis (Figures 5.3 and 5.4)

m/z 324.4 m/z 12.4 m/z 562.6 m/z 58 0.6 Rt(min) S/N Rt(mln) S/N Rt(min) SN Rt(min) S/N

Crude 1.84 901 23 14.89 266 15.82 32 Recrystallised 2.17 115 4.4 300 15.14 256 16.06 70

Peak Area (% of total area) m/z 324.4 m/z 342.4 m/z 562.6 m/z 580.6

Crude 149393804 (46.4) 5254287 (1.6) 162367249 (50.4) 5062358 (1.6) Recrystallised 5190259 (1.7) 73734232 (23.8) 216442600 (69.9) 14157290 (4.6)

138

100

80

8 60 c 03

§ 40

i 20 I 100

80

60

40

20

0

14.95 ' 39E7

14 87

10 Time (min)

15

NL; 5 48E6 Base Peak m/z = 100.0-1000 0

20

Figure 5.1 Total ion (TIC; Top) and base peak (BP; Bottom) HPLC/ESI-MS

chromatograms of the crude product of the thermal reaction of palmitic acid

with DETA in xylene solvent.

39

100

80

60

c u (—)

40 < > 20 ' CD 100 cr

80

60

40

20

15.16 1 79E7

15.14

10 Time (min)

NL: 7.65E6 Base Peak m/z = 100 0-1000.0

20


chromatograms of the recrystallised product of the thermal reaction of

palmitic acid with DETA in xylene solvent.

140

100 I T A 4 71E6

50

< 50

100

50

1:1-PI(46%) nvz= 323 9-324 9

5 0 RT 3 92 N L ^ r. . . B 1 71E5

Palmitic-monoamide A T V ^ s (1.6%) 341 9-342 9

^ ^ J 2:1-PI (50%) A ^

m 562 1-563 1

RT: 15.82 NL

Palmitic-diamide 2 06E (1.6%)

0 ~ r " I T " " i " " i " " [ " " i " " i ' " ' ' i " ' ' ' i "

I D 580 1-581 1

5 10 15 20 Time (min)

Figure 5.3 HPLC/ESl-MS extracted mass chromatograms from the crude product of

the thermal reaction of palmitic acid with DETA in xylene solvent: (A) 1:1-

PI {m z 324.4), (B) palmitic-monoamide (m z 342.4), (C) 2:1-PI (m z 562.6)

and (D) palmitic-diamide (m z 580.6).

41

100

50

RT: 2.17

I 100

< 50 > ^ 0 (T 100

1 RT: 4 40

—

50

0 100

50

0

1:1-PI (2%)

RT: 4.38

Palmitic-monoamide (24%)

RT: 15 14

2:1-PI (70%)

RT: 16.06

1,2- and 1,3-Palmitic-diamide (5%)

NL: 2 06E5 m/z = 323 9-324 9

NL: 245E6 m/z = 341 9-342 9

NL 7 18E6 m/z = 562 1-563 1

10 Time (min)

r, D ^ i e

15 20

NL: 409E5 m/z = 580.1-581 1

Figure 5.4 HPLC/ESI-MS extracted mass chromatograms from the recrystallised

product of the thermal reaction of palmitic acid with DETA in xylene

solvent: (A) 1:1-P1 {mz 324.4), (B) palmitic-monoamide (mz 342.4), (C)

2:1 -PI (m r 562.6) and (D) palmitic-diamide (m z 580.6).

142

In the crude product. 1:1-PI (m/z 324.4) was present at 46 % of the total peak area of the

four main ions and the 2:1-PI (pi/z 562.6) at 50 % (Figure 5.3 A and C). This was not

expected as Wu and Herrington did not report the formation of 1:1-PI or monoamide.

However, it was consistent with other syntheses of imidazolines conducted herein (Chapter

4). No ions could be observed or attributed to 2:l-PI-palmitic acid complex which was the

product reported by Wu and Herrington, although this may have been due to

disassociation of the complex to the protonated 2:1-PI {m/z 562.6) which was observed

(Figure 5.3C and 5.4C). The monoamide {m/z 342.4) and diamide {m/z 580.6)

intermediates were present (each 1.6 %). Only one peak was observed for the diamide {m/z

580.6) at 15.8 minutes (Figure 5.3D). No distinction could be made as to whether the peak

was due to the 1,2-diamide or the 1,3-diamide (or both) as the masses are isobaric.

The product recrystallised (from ethyl acetate) contained 70 % 2:1-PI {m/z 562.6) by total

peak area of the four main compounds (Table 5.2), whilst the 1:1-PI was ca 2 %. The

monoamide {m/z 342.4) and diamide {m/z 580.6) both showed an increase in relative

amounts to ca 24 % and 5 % respectively {cf 1.6 % in the crude product). This was

probably due to hydrolysis of the 1:1/2:1-PI during the recrystallisation (a boiling water

bath was used to heat the solution). A valley indicating two peaks was observed in the

extracted diamide mass chromatogram {m/z 580.6; Figure 5.5) of the recrystallised product

probably reflects some separation of the 1 - and 1,3-diamides.

143

100 ^

90

80

8 70 C CO

I 60

f 50

I 40 a:

30-.

20-.

10

0

RT: 16.06

RT: 15.52

NL: 4.09E5 m/z -580.1-581.1

Time (min)

Figure 5.5 Enlarged HPLC/ESI-MS extracted mass chromatogram of 1,3- and 1,2

palmitic-diamide {m/z 580.6) shown in Figure 5.4(D).

5.3.2 Solid phase thermal reaction of paimitic acid with dietityienetriamine

A solid phase thermal reaction of palmitic acid with diethylenetriamine was also carried

out by the method of Wu and Herrington*^ (Section 5.2.5). Compared with the solvent-

based reaction described in the preceding section (5.3.1) the reaction was carried out in two

steps and at a 2:1 molar ratio of fatty acid to DETA {cf one stage and a 1:1 molar ratio). In

the first step, 1,3-palmitic diamide (Wu and Herrington^ ) is reported to be synthesised by

heating the reagents at 150 ""C for 7 hr and is then isolatable by recrystallisation. In the

second step the 1,3-palmitic diamide is cyclized to 2:1-PI at 235 'C under reduced pressure

(30 mm Hg) for 2 hr (^0.5 hr Wu and Herrington^ ). Samples of the crude 1,3-palmitic

144

diamide, recrystallised 1,3-palmitic diamide and the recrystallised 2:1-PI products were

analysed by HPLC/ESI-MS and the total ion and base peak ion chromatograms are shown

in Figures 5.6, 5.7 and 5.8 respectively. Two major peaks are clearly seen in the total ion

(TIC) and base peak (BP) chromatograms of both the crude and recrystallised 1,3-diamide

products (Figures 5.6 and 5.7).The two peaks (3.9 and 15.8 min) are present in

approximately equal proportions in the crude product (Figure 5.6), whist the peak eluting

after 3.8 min was relatively much smaller in the recrystallised product (Figure 5.7). A

single peak with a small shoulder is observed in the recrystallised 2:1-P1 product with a

retention time of 15.1 min. Examination of the mass spectra of each component and mass

chromatography of ions indicative of 1:1-PI {m/z 324.4), monoamide {m/z 342.4), 2:1-PI

{m/z 562.6) and the diamides {m/z 580.6) (Figures 5.9, 5.10 and 5.11) allowed

identification of the components. Calculation of signal to noise ratios and peak areas for

both the crude and recrystallised products allowed the relative amounts to be estimated

(Table 5.3).

In the first step of the reaction, reported to be the formation of the diamide (Wu and

Herrington^ ), the crude product actually contains both monoamide {m/z 342.4) and a

diamide {m/z 580.6) (Figure 5.9B and D) with the monoamide at 51 % and the diamide at

44 % (Table 5.3). This was not expected as Wu and Herrington had not encountered the

monoamide. The 1:1-PI and 2:1-PI compounds were present in the crude product at 3.5 %

and 1.5 % respectively and therefore are not readily formed under the reaction conditions

employed (Figure 5.9A and C; Table 5.3). A single recrystallisation produced a mixture

that comprised 86.5 % diamide {m/z 580.6), 11.5 % monoamide {m/z 342.4). 1 % 1:1-PI

{m/z 324.4) and 1 % 2:1-PI {m/z 562.6) (Figure 5.10; Table 5.3). There does not appear to

be any detrimental effects fi-om the crystallisation procedure and therefore repeated

recrystallisations might allow the product to be purified further. The second step of the

reaction to convert the diamide to the 2:1-PI produced a 2:1-PI with ca 95 % purity (by

145

HPLC/ESI-MS) with 0.2 % 1:1-PI {m/z 324.4), 0.2 % monoamide {m/z 342.4) and 4.3 %

diamide {m/z 580.6) (Figure 5.11; Table 5.3) from a single recrystallisation. Conversion of

the diamide to imidazoline does not appear to be the problematic step of the reaction;

rather formation of the initial mono or diamide is more complicated than stated by Wu and

Herrington 89

Table 5.3 HPLC/ESI-MS peak retention times (Rt), signal to noise ratios (S/N) and

peak area data acquired from the extracted mass chromatograms for

protonated ions of: 1:I-PI {m/z 324A), monoamide {m/z 342.4), 2:1-PI {m/z

562.6), and diamide {m/z 580.6) for the crude and recrystallised palmitic-

diamide and recrystallised 2; 1-PI products of solid phase synthesis (Figures

5.9,5.10and5.11)

m/z 324.4 m/z Z4 (2.4 m/z 562.6 m/z Si )0.6 Rt(min) S/N Rt(min) S/N Rt(min) S/N Rt(min) S/N

Crude diamide 3.82 43 3.75 531 14.99 50 15.77 248 Diamide 3.81 27 3.81 263 14.88 32 15.69 198 2:1-PI 2.18 12 4.63 11 15.1 4561 16 94

Peak Area (% of total area) m/z 324.4 m/z 342.4 m/z 562.6 m/z 580.6

Crude diamide 6911107 (3.3) 109204991 (51.4) 2959222 (1.4) 93438432 (44.0) Diamide 1524770 (0.7) 26865167 (11.6) 2823968 (1.2) 199668674 (86.5) 2:1-PI 707887 (0.2) 528287 (0.2) 312749178 (95.3) 14056288 (4.3)

146

15.79

80 0.45

' 20E7

E 60

15.79 1100 NL: 349E6 Base Peak m/z = 100 0-1000 0

10 Time (min)

20


chromatograms of the crude palmitic-diamide product of the solid phase


147

15.70

§ 40 0.46

15 67

10 Time (min)

15

NL: 7 13E6 Base Peak m/z = 100 0-1000 0

20


chromatograms of the recrystallised palmitic-diamide product of the solid

phase thermal reaction of palmitic acid with DETA.

148

15.12

15.12 ^ 100

10 Time (min)

NL 2.17E7 TIC

NL: 1 08E7 Base Peak nVz = 100.0-1000 0


chromatograms of the recrystallised 2:1-PI product of the solid phase


49

100 RT: 3 82

I 50 a> a: 0

100

50

0 100

50

8 50 i l l O O

1:1-PI(3.5%)

A

0 0

Palmitic-monoamide (51%)

2:1-PI (1.5%)

RT: 14.99

RT: 15.77

Palmitic-diamide (44%)

" I " " I " " ! " " P " M " " [ " ' — ' — '

5 10 Time (min)

15

A 212E5 m/z = 323 9-324 9

NL: B 3 2 4 E 6

m/z = 341.9-342 9

NL: C 1 24E5

m/z = 562 1-563 1

D NL 338E6 m/z = 580.1-581 1

20

Figure 5.9 HPLC/ESI-MS extracted mass chromatograms from the crude palmitic-

diamide product of the solid phase thermal reaction of palmitic acid with

DETA: (A) 1:1-PI (mr 324.4), (B) palmitic-monoamide {mz 342.4), (C)

2:1-PI (m z 562.6) and (D) palmitic-diamide (m z 580.6).

50

100 RT: 3.81 NL A 611E4

50 I 1:1-PI(1%) nVz = 323 9-3249

| l O O q RT:3.81 NL: ^ Palmitic-monoamide B 9 37^5 I 5 0 | I (11.50/0) ^ = 3 , 2 3

l l o S RT: 14.88 C 1 28E5

50 2:1-PI(1%) m/z = 562 1-563 1

0 100

50 Palmitic-diamide (86.5%)

0 r" " " " I " " I" • ' I " " I • " ' I " • ' I " " I " " I '

0 5 10 Time (min)

RT; 15 69

6 7 4 E 6

580 1-581 1

Figure 5.10 HPLC/ESI-MS extracted mass chromatograms from the recrystallised

palmitic-diamide product of the solid phase thermal reaction of palmitic

acid with DETA: (A) 1:1-PI (mr 324.4), (B) palmitic-monoamide (m'z

342.4), (C) 2:1-PI (m z 562.6) and (D) palmitic-diamide (m z 580.6).

15

100

50

RT :2 .18 NL

1:1-PI(0.2%) . ^3^32,9

" RT 4 fi"? NL:

"E Palmitic-monoamide " m/z = I 50 .• (0 200)

i m n RT: 15.10 NL: , ©100 4 ^ 1 04E7 ° C ^ =

341 9-342 9

50 2;1-PI(95%) 562 1-563 1

0 100 RT. 16.00

50 Palmhic-diamide \ ^ (4.3/o) / \

^ 0 5 10 15 20 Time (min)

Figure 5.11 HPLC/ESI-MS extracted mass chromatograms from the recrystallised 2:1-

PI product of the solid phase thermal reaction of palmitic acid with DETA:

(A) 1:1-PI (mr 324.4), (B) palmitic-monoamide {mz 342.4), (C) 2:1-PI

(mr 562.6) and (D) palmitic-diamide (m r 580.6).

152

5.3.3 Infusion electrospray ionisation multistage mass spectrometry (ESI-MST)

analysis of the solvent and solid phase synthesis products

The m/z values identified in the HPLC/ESI-MS analyses of the crude and recrystallised

products were consistent with protonated ions for 1:1-PI {m/z 324.4), monoamide (m/z

342.4), 2:1-PI (m/z 562.6) and the diamides (m/z 580.6) although no structural information

was obtained to confirm the assignments. Multistage mass spectrometry allows

characteristic collision induced dissociation (CID) fragmentation of a precursor ion in an

MS' full scan spectrum. As previously shown in Chapter 2, CED MS" fragmentation

pathways can allow identification of unknown compounds as well as unambiguous

identification of known compounds previously characterised from pure standards. The

crude and recrystallised products from the solvent and solid phase syntheses were therefore

also analysed by infusion ESI-MS" in order to obtain structural information which would

allow identification of the products and by-products. Infusion of the sample into the mass

spectrometer was used in preference to either HPLC or flow injection as a continuous flow

of sample allows a wider range and optimisation of CID experiments to be carried out

without interruption of the sample flow.

5.3.3.1 Infusion electrospray lonisation multistage mass spectrometry (ESI-MS") analysis of

the crude reaction products of the thermal reaction of palmitic acid with


Figure 5.I2A shows the MS' fiill scan mass spectrum of the crude product over the mass

range m/z 50 - 1000, with the instrument optimised (auto-tuned) on the ion at m/z 324A.

Ions with relative abundances consistent with protonated ions for l:l-PI (m/z 324.4),

monoamide (m/z 342.4), 2:1-PI (m/z 562.6) and the diamides (m/z 580.6) which were also

observed in the HPLC/ESI-MS mass chromatograms (Section 5.3.1) were identified.

Changing the full scan mass range to m/z 50 - 700 and again auto-tuning on m/z 324.4

(Figure 5.12B), the relative abundance of m/z 324A increases relative to m/z 562.6. This is

153

due to instrument bias towards higher masses, particularly when wide mass ranges are

used. For all MS" experiments the instrument was auto-tuned on the ion of interest prior to

analysis. High resolution ZoomScan mass spectra were acquired of the two prominent ions

{m/z 342.4 and m/z 562.6; Figure 5.13) shown in the ftill scan spectra. For both ions, base

line resolution with a peak width of m/z 1, which is indicative of singularly charged ions.

Multistage mass spectrometry on the MS' m/z 324A and m/z 562.6 precursor ions (Figure

5.12B) was carried out.

Figure 5.14A shows the MS^ CID mass spectrum of m/z 324.4, in which a m/z 281.4 ion is

the only major ion product of decomposition. A m/z 307.4 ion at ca 1 % relative abundance

was also observed. MS^ CID of m/z 281.4 (Figure 5.143) produces a series of ions

differing by 14 Da (CH2 group) with m/z 97.1 as the most abundant. The MS^ and MS^

product ions are consistent with the previously proposed ion trap CID fragmentation

pathway for 1:1-imidazolines (Chapter 2; Section 2.3.2.3) and is shown in Figure 5.14C for

the 2:1-PI. Identical MS^ and MS^ spectra to those obtained for the m/z 324A ion (Figure

5.14A and B) were obtained (Figure 5.15A and B) from the CID of the m/z 562.6 precursor

in Figure 5.12B. Again this fragmentation pathway (Figure 5.15C) is consistent for 2:1-

imidazolines as previously proposed (Chapter 2; Section 2.3.2.3) and shows that MS^ CID

fragmentation is at the same position (N-1) on the imidazoline moiety regardless of

whether the parent ion is the 1:1- or 2:l-imidazoline. The optimum activation amplitude

(AA; the percentage Normalized Collision Energy™) to induce fragmentation in the ion

trap, is the same for both precursor ions (MS^; 42 % AA and MS^; 53 % AA).

154

100-1

g50 c CO •o c 3 a 0

1:1-PI 324.4

2:1-PI 562.6

97.1 180.4 281,5 4.

Palmitic -monoamide

342.3 534,5

I " " t " " i • '"I " • " M " • • I " " I " " [ " • ' I

200 400

Palmitic-diamide 580.5 ^ 7 ASA 903.0 983.4

I " " 1 " " I " ' - I " " I' I I I " • ! • " ' I " " I

CD

600

•ôo-i

50

324.4

97.1 166.5 214.0 281 5

800

562.6

1000

342.3 434.4 534.5

B

646.5 t " ' l " M " V t ' " l ' " t ' " f " ' | " ' t ^ " r " 4 ' " l ' " | ' " l ' " t " ' l " ' l " ' | " ' L|'ln|nnLin.n|ni|nniM|

100 200 300 400 m/z

500 600 700

Figure 5.12 Infusion ESI-MS mass spectra of the crude products of the thermal reaction

of palmitic acid with DETA in xylene solvent. Positive ion fiill scan spectra:

(A), m/z 50 - 1000 (capillary voltage (+3.88 V), 1'* octapole (-1.39 V), 2™*

octapole (-1.39 V) and tube lens (-39.24 V) and (B), m/z 50 - 700 (capillary

voltage (+2.85 V), 1' octapole (-1.47 V), 2"** octapole (-6.96 V) and tube

lens (-33.22 V). Both spectra acquired after auto-tuning on ion m/z 324A at

each m/z range. The differences illustrate changes in response dependent on

m/z range and tune parameters.

55

1 < (D

. >

100^

90

80

7 0 ^

60

50 ;

40 i

30^

20

1 0 ^

324.4

322.4

325.4

326.3 l " " i " " i " " i " " r " " | ' " " i ' ' ' " i " " i " i n i

320 325 m/z

100

90 1

80 {

70^

60

50^

40-j

30 i

20 1

10^

562.6

563.6 r

l " " l " " | " " l " ' M ' ' ' " ' l ' ' ' " l " " | " ' ' ^ i | " " t

560 565 m/z

Figure 5.13 ESI-MS ZoomScan mass spectra of the 1:1-PI ion (Left) and 2:1 PI ion

(Right) shown in the full-scan spectrum (Figure 5.12B).

156

100

50 i

281.4

212.8 279.8_i307^ 324.4 . | . . . . | . , . . , . . . . | , , . . | , . , , | . . . . | i . . . | . . . . | , , M | , i , , | M i i | i n i , i . . i | i i . , | . , . . | , u . | . . . . | ^ . . . | , i . Y i i . | . i . i | i l i i | . i , , | n i , | . , . i , i . , . | , M , | , . n | i

MS'

150 200 250 300 350 400

S. 100^

50 i

97.1

B MS'

111.1 139.1 195.3 209.3 . . . . 1 . I f" , 2 0 J . 5

281.5

l " " j ' ^ " i - " i | i " f i " " | " " i " ' ^ ' t " " r " ' i i i ^ ' l JTTITJTTTTJTTT

381.0 ]jl.lHI..-|llHt.iU|lNllllH|l|]||iMHIIIIflM.|LLiH

100 150 200 250 m/z

300 350 400

MS' HNn. , n h

Loss of ^ N H 2

MS^ Precursor ion

m/z 324.4

MS^ Product ion

m/? 281.4

MS' Loss of alkyi groups

H N n ^ ^ N H

MS^ Product ion

m/z ^7 A

Figure 5.14 ESI-MS" mass spectra and proposed fragmentation pathways of the 1:1-PI

precursor ion {m/z 324.4) in the full-scan spectrum (Figure 5.12B). (A) MS^

of precursor ion m/z 324 A (42 % AA), (B) MS^ of product ion m/z 281.4

(53 % AA) and (C) proposed CID fragmentation pathway.

157

100 ^

01

E E 0 < .1 1

281.4

181.0 223.3

MS-

282.3 _324.3 426.4 465.1 562.7

200 300 400 500 600 700

97.1

50 i

B MS-

111-1 167.2 f |iii.j i iViiMii^'ii i i ir\i i |iiil|rrir]l

181.3 195 3 281.4

| . i / ( |ni .pn.pL1. | i i . lVH) | i1i . | in1 | i iL i | lL . i | i iVj . . i i ; in . | f l i i |Ni1 | i i i i |^ i„| ini | i i i i( l iM|i iN| iMi | i in| i i i i ,ni i | i in^.n . | i i i i^

100 150 200 250 m/z

300 350 400

HNs.^NH

Loss of

MS' Precursor ion

m/z 562.6

MS^ Product ion

m/z 281.4

MS'

HNs.^NH

MS^ Product ion

m/z 97 A

Figure 5.15 ESI-MS° mass spectra of the 2:1-PI precursor ion {m/z 562.6) in the full-

scan spectrum (Figure 5.12B). (A) MS^ of precursor ion m/z 562.6 (42 %

AA). (B) MS^ of product ion m/z 281.4 (53 % AA) and (C) proposed CfD


158

5.3.3.2 Infusion electrospray ionisation multistage mass spectrometry (ESI-MS") analysis of

the recrystallised product of the thermal reaction of palmitic acid with


Figure 5.16 A and B show the MS' full scan mass spectra of the recrystallised products of

the solvent synthesis, over the mass range m/z 50 - 700, with the instrument optimised

(auto-tuned) on the ion at m/z 562.6 (Figure 5.16A) and m/z 342 A (Figure 5.16B). There is

only a small change in response (c.a. 25 % to 35 % relative abundance) for the lower mass

ion due to a smaller difference between tuned masses (A m/z 220) and no change in full

scan mass range (CM. Figure 5.12A and B). Two prominent ions were observed with m/z

values and relative abundances consistent with protonated ions of palmitic-monoamide

(m/z 342.4), and 2:1-PI (m/z 562.6) observed in the HPLC/ESI-MS mass chromatograms

(Section 5.3.1) of the recrystallised products. The ions for 1:1-PI (m/z 324.4) and the

diamide (m/z 580.6) were also observed in the spectra at < 5 % relative abundance.

ZoomScan, MS^ and MS^ mass spectra (not shown) of the MS^ precursor ion m/z 562.6,

were identical to those obtained for the same m/z value in the crude products discussed in

Section 5.3.3.1 and confirmed the ion to be due to 2:1-PI. The m/z 342.4 ion which had

increased in abundance during and after recrystallisation was at a relative abundance which

allowed multistage experiments to be carried out, which was not the case in the spectra of

the crude product (Figure 5.12A and B). The ZoomScan spectrum of m/z 342.4 (Figure

5.17) showed base-line resolution with a peak width of I Da indicative of '^C/'^'C isotopes

of a singularly charged ion. MS^ CID of the precursor ion w/z 342.4 (Figure 5.18A)

resulted in an m/z 324.4 product ion, which on MS^ and MS'* (Figure 5.18C and D)

fragmented identically to that of the 1:1-PI (m/z 324.4) precursor ion in the crude product

(Figure 5.14 and section 5.3.3.1). This is consistent with the loss of water (18 Da) from

protonated palmitic-monoamide with cyclisation to protonated 1:1-PI. The MS^

fragmentation does not allow distinction of the 1-monoamide (Structure III, Figure 3.1) or

the 2-monoamide (structure IV, Figure 3.1), to the precursor palmitic-monoamide ion (m/z

159

342.4) to either the precursor palmitic-monoamide ion {m/z 342.4), therefore, a proposed

fragmentation pathway is shown (Figure 5.19) assuming that ion trap MS^ CID is the same

for both 1- and 2-monoamides.

100-3

50 i

§ 0 (0 •a c

Si 00 a>

50 i

I:1-PI Palmitic -monoamide

342.4 97.3 157.9 214.0 282.^ 384.4

2:1-PI 562.6 ^

Palmitic-diamide

478.3 534.7 l " ' l " T " ' " ' ' " ' ' " ' ' " ' l " ' l " ' ' " ' ' " ' ' " ' r " l I ' l ' " ! ^ " ! " | i " | " r | i i i | M . | i . - | , . i . | i l i i f i . . ^ i i . | - i n | . i i | . . i |

580.5 620.1

100 200 300 400 500 600 700

562.6

342.3

97.4 214.,1 281,.5_324.5 384.4 462.1 534.6 r T T T T T T J T T T T T T T T r n T T T T p T T ^ ^ ^

B

^ - ? ° \ l 9 . 7

100 200 300 400 m/z

500 600 700

Figure 5.16 Infusion ESI-MS mass spectra of the recrystailised product of the thermal

reaction of palmitic acid with DETA in xylene solvent. Positive ion full

scan spectra: (A), auto- tuned on ion m/z 562.6 {m/z 50 - 700, capillary

voltage (+30.15 V), 1 ' octapoie (-2.42 V), 2nd octapole (-5.93 V) and tube

lens (-23.12 V) and (B), auto-tuned on ion m/z 342.4 {m/z 50 - 700,

capillary voltage (+30.15 V), l " octapole (-1.17 V), 2°^ octapole (-6.88 V)

and tube lens (-27.19 V). Spectra illustrate changes in response dependent

on m/z auto-tuned values.

160

342.3 8l ^ 0 0 ^ CO

c

< 50 (D

. 5 343.3

344.3

338 340 342 344 miz

346

Figure 5.17 ESI-MS ZoomScan mass spectrum of the palmiric-monoamide ion shown in

the full-scan spectrum (Figure 5.16B).

100 ^

50

104.2

324.4

282.3 !'j ] I 1 J 11 t t t I I I I I I

MS'

^ 5 . 2 V i l l i i i f i

100

§100 c

.1 ID

cr

50

. . i i | i i i i | i . . i | . i i . | i i i 4 i i . Y i i . | i i i i | i n . | u , i | . i i i | i i i i | i i i i | i i . i ) F i H | i n i | i i i i | . i i i | . U i | i i i . | f i i i | . . i . | . . i i | i i M | u . i | . . . . |

150 200 250 300 350 400

281.4

240.0 264.3

B MS'

324.3 i | . u . | i i n | i i n | i i n | n . i | i i i i | i . . . | i i i i | i i i i | i . i . | i . M j i . i . | i i N | i i i i | i i n | n i i | i i i . | i i i i | L i H | l u i | L i n | i i i 1 | M i i | i l u , i i i i | i i n ^ i i . i | i i i i | ^

100 150 200 250 300 350 400

100

50 i

97.1

MS'

^ . , n | n n , i . n | n n | , , , , | , , M | „ , , | M . . | . . . . , i . . . | . , . . | n n | , , , , | , , , , ; . . , , | , , , Y ' ' l | l " M ' " N ' ' - ' l " - ' | ' - " l ' ' " l " ' - | ' " M - " ' | - ' ' - | ' " ' l "

100 150 200 250 m/z

300 350 400

Figure 5.18 ESI-MS" mass spectra of the palmitic-monoamide precursor ion {m/z 342 A)

in the full-scan spectrum Figure 5.16B. (A) MS^ on precursor ion m/z 342A

(30 5 AA), (B) MS^ on product ion m/z 324.4 (42 % AA) and (C) MS"

product ion m/z 281.4 (54 % AA).

161

s MS^ Precxirsor ion

m/z 342.4

MS'

Loss of HjO

_ V MS' H N y N ^ ^ 6 ^ N H 2 HN> NH

Loss of

Loss of alky! groups

H N n ^ ^ N H

MS^ Production

m/z 324A

MS^ Product ion

m/^ 281.4

MS"* Product ion

m/z 97 A

Figure 5.19 Proposed CID fragmentation pathway of compounds assigned as 1- and 2-

monoamides.

162

5.3.3.3 Infusion electrospray ionisation multistage mass spectrometry (ESI-MS") analysis of

the crude and recrystallised palmitic-diamide products and the recrystallised 2:1-PI

product of the solid phase thenmal reaction of palmitic acid with diethylenetriamine

The MS* fiill scan mass spectra (over the mass range m/z 50 - 700) of the crude and

recrystallised palmitic-diamide intermediate products (Figure 5.20A and B) and the

recrystallised 2:1-PI final product (Figure 5.21), showed ions with relative abundances

consistent with the protonated ions for 1:I-PI (nx/z 324.4), monoamide (rn/z 342.4), 2:1-PI

{m/z 562.6) and the diamide {m/z 580.6) observed in the respective HPLC/ESI-MS mass

chromatograms (Section 5.3.1). Multistage MS" analysis of the base peak ion, m/z 342.4 in

the crude palmitic-diamide (Figure 5.20A) and the second most abundant ion in the

recrystallised palmitic-diamide product (Figure 5.20B), produced M S \ MS^ and MS'*

spectra (not shown), identical to those of the corresponding ions in the recrystallised 2:1-PI

product of the solvent based synthesis (Figure 5.18; Section 5.3.3.2). They can therefore

be assigned as arising from decomposition of the protonated ion, of the palmitic-

monoamide (either 1- or 2-monoamides). MS" analysis of the almost exclusive ion, m/z

562.6 (Figure 5.21), produced MS^ and MS^ mass spectra (not shown) identical to those of

the corresponding ions in the recrystallised 2:1-PI product of the solvent based synthesis

(Figure 5.18; Section 5.3.3.2) and can be assigned as due to the protonated 2:1-PI ion. The

ion m/z 580.6 is the base peak ion in the spectrum of the recrystallised palmitic-diamide

product (Figure 5.20B) and second most abundant ion in that of the crude palmitic-diamide

product (Figure 5.20A). MS^ MS' and MS" CID spectra of the m/z 580.6 ion were

identical in both the crude and recrystallised palmitic-diamide products and are discussed

below for the recrystallised palmitic-diamide product (Figure 5.20B). The ZoomScan

spectrum of the ion m/z 580.6 (Figure 5.22) shows base-line resolution with a peak width

of m/z 1 indicative of a singularly charged ion. MS^ CID of the precursor ion m/z 580.6

(Figure 5.23A) resulted in four significant product ions {m/z 282.3 (95 %), m/z 299.2 (40

%), m/z 562.5 (55 %) and m/z 563.5 (100 %)). The ions m/z 562.5 and m/z 563.5 are shown

to be distinct separate ions in the enlargement of the spectrum (Figure 5.23B) and since the

163

higher mass ion is ca 40 % more abundant, this cannot be due to a isotope. Ion m/z

563.5 is due to loss of 17 Da from the precursor ion m/z 580.6 (Figure 5.23A), which is the

mass expected for the 1,3- and 1,2-palmitic diamides (structures V and IV respectively, R

and Ri = C15H31, Figure 3.1). Although both amides are isobaric, only the 1,2-diamide can

lose ammonia (17 Da) by MS^ CID to give the m/z 563.5 product ion observed in Figure

5.23. MS^ CID of the m/z 563.5 involves an approximately symmetrical cleavage to m/z

282.3 (Figure 5.24), which on MS'* CID produces a m/z 95.2 ion (Figure 5.25). The m/z

562.5 MS^ CID product ion observed in Figure 5.23A and B, can be accounted for by loss

of water from a diamide and cyclisation to form the protonated 2:I-PI ion. Indeed, this is

confirmed by MS^ and MS"* CID spectra (Figures 5.26 and 5.27 respectively) in which

product ions corresponding to a ion trap CED fragmentation pathway previously proposed

for 2; I-PI (Figure 5.15C and Chapter 2; 2.3.2.3) are observed. An m/z 562.5 ion is also

observed as the base peak in the MS^ CID spectrum (Figure 5.24), which might be

construed as evidence of loss of hydrogen radical from m/z 563.5 (and therefore loss of a

hydroxyl radical rather than ammonia from the diamide precursor). However, loss of a

hydrogen radical following loss of hydroxyl was ruled out on the basis that MS'* and

MS^ CID (not shown) of the m/z 562.5 ion produced spectra identical to that consistently

obtained for protonated 2:1-PI proposed by CID fragmentation (Figure 5.15C and Chapter

2; Section 2.3.2.3). It is suspected that the m/z 562 ion is in fact not a CID product ion at all

since it was also present at 0% activation amplitude (AA) and the actual ion count

remained constant at 0, 31, 33 and (the optimum) 35% AA. Rather, it is suggested that the

m/z 562.5 ion was coincidentally isolated with the m/z 563.5 ion. Unfortunately attempts to

prove this by reducing the isolation width from the normal m/z 1 to m/z 0.9 resulted in

lower relative abundances for all ions and even lower isolation width values resulted in

trapping of too few ions and signal instability. However, in a similar experiment with a

oleic acid derived diamide {m/z 632.6; Chapter 4, section 4.3.8) the corresponding M-18

ion {m/z 614.6 cf 562.5) was not present in the MS^ spectrum (Appended; Figure A.4)

164

which supports the suggestion that 562.5 was not a CID product ion. All other equivalent

MS° spectra (Appended; Figures A.4 - A.7) of the MS^ product ions of oleic-diamide (ni/z

632.6; Appended; Figure A. 3) are identical except for the difference in mass (52 Da) and

support the fragmentation pathway for l,2-/l,3-diamides.

The MS^ CID spectrum (Figure 5.28) of the second most abundant product ion (jn/z 282.3,

95 %) of MS^ CID on the m/z 580.6 precursor (Figure 5.23A) was identical to that of the

corresponding MS'' product ion from m/z 563.5 ((Figure 5.25). Also the MS^ CID

spectrum (Figure 5.29) of the fourth most abundant product ion {jn/z 299.2, 40 %)

produced an m/z 282.3 ion by loss of ammonia (17 Da), which on MS'* CID was identical

to that described in the previous sentence.

165

100

50 8 C

c

342.3

1:1-PI

2 8 2 ^ 87.0 180.9 21.3.9

I 100-1

50 i

100 JL4

Palmitic -monoamide

Palmitic-diamide

580.5 2:1-PI

562.6 478.3 608.5 682.9

, . . . , M . ^ . M | . M ^ L L I | l l l | ' U . | i n t l M j l L I | n . i i l . | M . | L n | l l t | , M J . . H - . M i - . L L j l M | M H . n | n . | L . H

200 300 400 500 600 700

580.5

342.3

116J 192.8 222.6 282.4 T " l " ' i ' " l " ' l ' " ) " ' l ' " l " ' l '

430.9 562.7

B

608.5 664.5 ' i ' " i r ' M '

100 200 300 400 m/z

| l . l | . l l | I I L | . l l | I H | . M p . l | ' l l . | l 1 l | I I H I I I | l l l | I M |

500 600 700

Figure 5.20 Infusion ESI-MS mass spectra of the crude and recrystallised palmitic-

diamide products of the solid phase thermal reaction of palmitic acid with

DETA. Positive ion full scan spectra: (A), crude product (auto- tuned on

ion m/z 580.6, m/i 50 - 700, capillary voltage (+42.30 V), l " octapole (-

2.64 V), 2nd octapole (-6.44 V) and tube lens (-19.05 V) and (B),

recrystallised product, (auto-tuned on ion m/z 580.6, m/z 50 - 700, capillary

voltage (+22.10 V), l " octapole (-2.86 V), 2"^ octapole (-5.93 V) and tube

lens (-23.12 V).

166

100

9 0 -

80 ^

70

6 0 ^

50--

40--

30 \

2 0 ^

10

0

2:1-PI 562.6

97,1 149.2 226,7 281 5 342,4 413,4 442.9 534,7 111111

Palmitic-diamide

580.5 L-r 640.7

100 200 300 400 m/z

500 600 700

Figure 5.21 Infusion ESI-MS mass spectrum of the recrystallised 2:1-PI product of the

solid phase thermal reaction of palmitic acid with DETA. Positive ion full

scan spectra: (auto- tuned on ion m/z 562.6, m/z 50 - 700, capillary voltage

(+24.08 V), 1=" octapole (-2.93 V), 2nd octapole (-6.37 V) and tube lens (-

27.05 V).

167

100

90

80

70 i § 6 0 ^ (D ^

I 5 0 ^

I 40

I 30

20

10^

580.6

581.6

582.6 583.6

576 578 580 582 584 m/z

Figure 5.22 ESI-MS ZoomScan mass spectrum of the palmitic-monoamide ion shown in

the full-scan spectrum (Figure 5.21).

168

100

90

80

CO

I 60 <

S 40

30

20

10

0

282.3

299.2

I 111 [ 1 1 1 1

200 300

324.4

342.2

563.5

562.5

436.6 536,9 580.4

" ' I ' " I ' " I " ' I " ' I"' 1 1 " I " 1 1 ' " r " I •" 1 1 " 1 1 " P " I ' " I • • ' J " • I ' " I " ' I " ' I 400 500 600 700

m/z

8 C (D "D C E < o .2 ro (D

100^

90--

80

70

60

50--

A0--

30--

20--

10

563.5

562.5

561.4 564.5

B

|""r"'l""l""| '"' l""l""t""| '"' '"^'t""l ' i"|""l ' t..iipiii|ninnu|iin|HU|iL.nLiM|MiY'"l 556 558 560 562 564

m/z 566 568

I j l M I | N I I

570

Figure 5,23 ESI-MS^ CID mass spectrum (A) of the palmitic-diamide precursor ion, m/z

580.6 (40 % AA) in the full-scan spectrum (Figure 5.20B). (B) Shows an

enlarged view of ion at m/z 563.6.

169

100

90-.

80--

70--

8 60 CD

1 50

0 40

1 30 a.

20 10-3

0

562.5

282.3

212.2 | " M ' " I ' " I

325.4 353-8 446.5 491.6

563.5

I"' I ' " I ' " | " M " ' 1 ' 1 1 1 ' " I " ' 1' 1 1 1 1 " r " 1 " - 1 ' 1 ' " ) " ' I

200 300 400 500 600 700 m/z

Figure 5.24 ESI-MS' CID mass spectrum of the product ion, m/z 563.5 (35 % AA) in

the MS^ spectrum (Figure 5.23).

1 0 0 t

9 0 ^

80

70

i 6 0 ^

1 50

I 40

1 30

20 i ô--

0

95.2

109.0

138.1 127.9

100

184.5 156.3

282.2

, i . . . | . . i . , . . . . , , . , , , . r , , , . , . , | , , . , | i L i < . ) i M i | i i i i | i i i i | M i i | i r i i | i i i i ] Y i i i p i T i j T r n | i i i i | i , . . , . . M , . . M |

150 200 250 300 350 m/z

Figure 5.25 ESI-MS'* CID mass spectrum of the product ion, m/z 282.3 (45 % AA) in


170

100-z

90-.

80

7 0 ^

8 60

I 5 0 5

< 40 o I 3 0 ^ S

205 10

0

281.4

T-n-rj 223.3 324.5 562-5 616.8

200 300 400 500 600 700 m/z

Figure 5.26 ESI-MS' CID mass spectrum of the product ion, m/z 562.5 (42 % AA) in


100 3

90 5

80

70

8 60

I 50 D < 40 ? 1 3 0 ^

205

10

0

97.1

84.1

281.5

111.0

167.3 181.3

125.1

| i S ' u | . , l , ' | „ i , | T n , | M ' i i | m , - , . n i | M , | , M n | „ i . | ^ , n | , A i | . , u V , . . , . ^ . i , i . , ^ |

195.2 223.4 249.0

1 I I I I 1 1 I M I 1 I 1 I I I 1 I 1

100 150 200 250 300 350 m/z

Figure 5.27 ESI-MS" CID mass spectrum of the product ion, m/z 281.3 (53 % AA) in


171

100

90

80

170 CD

I 60 < I 50

30

20

10

0

95.2

282.2

9Z0

123.1

137.2 238.1

ILL\ II

198.1

225.9 i j i ' l

286.9

100 150 | n i t j M M t l L M | I L L l f j l f f | M i i j ] ] l l t ] M L | l l M | > l f t | L l l l | l l M t i m | i m | I L I H L L H | l J J H L I I H I M H U J I | I I L I |

200 250 m/z

300 350 400

Figure 5.28 ESI-MS' CED mass spectrum of the product ion. m/z 282.3 (47 % AA) in


100

90

8 0 ^

70 i 60-.

50-

40

30

2 0 ^

^0--

0

282.3

298.9

l ' ' ' ' i ' ' 'T' ' ' l ' ' ' ' l ' ' ' ' l ' ' ' ' l ' ' ' ' l ' ' ' ' l ' ' ' ' l" ' ' i '" ' l ' ' ' ' l ' ' ' ' l ' ' ' ' l ' ' ' ' l ' ' ' ' l ' ' '1 ' ' 'M'' 'M- ' - 'r ' ' ' '4'"' | '"M'''4-' '^"

348.0

100 150 200 250 300 350 m/z

Figure 5.29 ESI-MS' CDD mass spectrum of the product ion, m/z 299.2 (28 % AA) in


172

From all the MS° CID spectra obtained for the protonated 1,2- and/or 1.3-diamides (m/z

580.6 (palmitic derived) and m/z 632.6 (oleic derived)) precursor ions (Figure 5.23A and

Figure A.2 (Appended)), two ion trap CID fragmentation pathways can be deduced (Figure

5.30). It is proposed that one pathway is derived from the 1,2-diamide which would have a

distinct MS^ CID product ion, from loss of ammonia (MS^b; Figure 5.30). The second

pathway for 1,3-diamides would not result in MS^ CID loss of ammonia, but would

involve production of M-18 ion via loss of water with cyclisation (MSâ; Figure 5.30). It is

also suggested that the MS^ CID product ions MS^c and MSM ((Figure 5.30) might be

more abundant from the symmetrical 1,3-diamides. Evidence to support the presence of

both 1,2- and 1,3-diamides can be shown in the HPLC/ESl-MS m/z 580.6 (palmitic-

diamide) extracted mass chromatograms (Figure 5.5 and Figure 5.11) which show LC

resolution of two compounds. When the relative abundance of the components is low,

some resolution of the two diamides is observed. At higher abundances the peaks co-elute.

An improvement in the HPLC/ESI-MS resolution of the 1,2- and 1,3-diamides should

confirm this proposal and allow online HPLC/ESI-MS" analysis of the individual

compounds to be carried out.

173

H H

d d

1.3-Palmitic-diamide 1,2-Palmitic-diamide

MS^ Precursor ions: m/z 580.6

a.candd | MS^ a, b, c and d

b LossofNHa

From 1.2-Palmitic-diamide

V H

MS^ Product ton

m/z 562.5

As Figure 5.15C

R = C , , H ^

MS^ Product ion

m/z 563.5

MS^ Product ion MS^ Product ion

m/z29S.2 m/z 282.3

MS'

0

H2

MS^ Product ion

m/S? 282.3

Loss of NH.

m/z 95.2

Figure 5.30 Proposed CID fragmentation pathway of compounds assigned as 1,2- and

1,3-diamides.

174

5.3.4 Fourier tramform infrared (FT-IR) spectroscopy analysis of the solvent and

solid phase synthesis products

Fourier transform infrared spectroscopy has been widely^''^ ' ' *' ^"^ used to identify and

to characterise imidazoline and its related amides. Identifications have been based on the

characteristic absorption frequencies of amides 1680 - 1640 cm * (C=0 stretch; Amide I

band) and 1560 - 1530 cm"' (NH bend; Amide II band)) and imidazolines (1610 - 1600

cm''; >C=N stretch).'^'* The FT-IR spectra of the solvent and solid phase crude and

recrystallised products (Appended; Figures A.8 - A. 12) showed the respective

characteristic bands for amides and imidazolines (Table 5.4). No appreciable differences

could be determined between the comparable solvent and solid phase 2:1-PI products.

Although the HPLC/ESI-MS mass chromatograms and MS" spectra of the crude 2:1-PI

(solvent synthesised) and palmitic-diamide (solid phase synthesised) products showed ca

50 % each of the 1:1 and 2:1 molar ratio of fatty acid/DETA imidazoline or diamide

products, very little difference could be observed between IR spectra of the crude and

recrystallised products. The only significant difference was a very weak peak at 1506 cm '

in the spectra of both the crude 2:1-PI and diamide products which was not observed in the

spectra of the recrystallised products. This peak is in the range for NHj^ deformation (1530

- 1490 cm"'; amine salt)'^'* and both crude products were shown by HPLC/ESI-MS to

contain amine compounds (1:1-PI and palmitic-monoamide, solvent and solid phase crude

products respectively). The peak could be evidence for the fatty acid salt of 1:1-PI or

palmitic-monoamide, although the corresponding -COO' anti-symmetrical'^'* stretch peak

between 1600 - 1590 cm"' is not observed.

175

Table 5.4 Fourier transform infrared spectra, characteristic absorption frequencies

observed for the solvent and solid phase synthesis products of thermal

reaction of palmitic acid with DETA

Characteristic Absorption band Amide Imidazoline SOLVENT SYNTHESIS C=0 (u/cm') N-H (u/cm') >C=0 (v/cm')

Crude 2:1-PI 1645 1550 1608 Recrystallised 2:1-PI 1639 1552 1606

SOLID PHASE SYNTHESIS Crude palmitic-diamide 1639 1562 Recrystallised -palmitic-diamide 1639 1565 Recrystallised 2:1-PI 1643 1550 1608

5.3.5 Nuclear magnetic resonance (NMR) spectroscopy analysis of the solvent and

solid phase synthesis products

^H Nuclear magnetic resonance spectroscopy (*H NMR) has been used to characterise the

structures of imidazolines and amides."* * ** ^ The spectrum (Appended; Figure A. 13) of

the 2:1-PI product of the recrystallised solid phase synthesis (Section 5.2.5) and the

spectrum of the 2:1-PI produced by solvent synthesis (Chapter 4, section 4.2.4.3; not

shown) were similar and the chemical shifts were in general agreement with those for 2:1-

imidazoline published previously.^ ' ^ '®' ^ The characteristic proton of the amide group is

observed as a broadened signal at 6.5 ppm. The CH2-N=C protons of the imidazoline ring

are observed as a multiplet about 3.7 ppm, whilst the resonance of the ring C H 2 - N <

protons (multiplet) overiap with the > N - C H 2 - C H 2 - N - protons (triplets) between 3.0 and 3.5

ppm.

' H NMR spectra of the solid-phase synthesised palmitic-diamide (Section 5.2.5;

Appended; Figure A. 14) and a oleic-diamide formed from hydrolysis (during storage) of

176

2:1-oleic imidazoline (Chapter 4, section 4.3.8, Appended; Figure A.7) are consistent with

a 1,3-diamide (structure V, Figure 3.1)."'^^®^ The amide protons are observed as a

broadened signal at 6.5 and 6.0 ppm (1,3-palmitic and 1,3-oleic diamide respectively). The

C H 2 - C O and - C H 2 - N - C H 2 - protons are observed as triplets about 2.11 (2.20) and 2.66

(2.7) ppm respectively and the -CH2 -N-CO protons as a quartet at 3.3 (3.2) ppm.

Interpretation of ' H N M R spectrum (not shown) of the 2:1-PI product from the solvent

synthesis (section 5.2 4) was not possible due to impurities (as shown by HPLC/ESI-MS)

and ftirther purification is required for *H NMR structural interpretation.

5.3.6 Reaction intermediates and patltways of solvent and solid phase thermal reaction

of palmitic acid with DETA

The aim of repeating the synthesis originally described by Wu and Herrington^^ was

predominantly to obtain pure palmitic-diamide and 2:1-PI. Subject to improved

recrystallisation procedures, this was achieved. It was apparent however, that the

mechanisms proposed by Wu and Herrington for the solvent-based and solid phase

reactions require modification in the light of the results obtained herein. Only the final

recrystallised reaction products were analysed by Wu and Herrington by FT-IR, ' H NMR,

MS, NP-HPLC and ShifF base reactions by UV. Neither crude final products or reaction

sub-samples were examined. The important mono-amide and l:l-imidazoline

intermediates were therefore not detected. Mono-amide and l:l-imidazoline intermediates

were detected herein by HPLC/ESI-MS and ESI-MS° analysis of the crude and

recrystallised products of the solvent and solid phase syntheses.

An important consideration in determining the reaction mechanisms and intermediates is

the relative reactivities of the primary and secondary amino groups of DETA. In general,

the secondary amino group of polyamines has higher nucleophilicity with most

177

electrophilic reagents^ . However, the primary amino groups can be more reactive due to

steric factors of the carbonyl group to attack by the nucleophile^^•^^ Even though MS°

analysis of the palmitic and oleic diamide products (Section 5.3.3.3) showed evidence for a

primary amine group (1,2-diamine), currently the HPLC/ESI-MS and MS° methods do

not distinguish between primary, 1-monoamine or secondary, 2-monoamine intermediates.

Without solvent the thermal reaction of fatty acid with DETA appears to proceed via three

main stages; viz, salt, mono/diamide and imidazoline formation (Figure 5.31). Each stage

requires higher temperatures to overcome the intermolecular bonding and to allow the

correct orientations of the reaction centres and configuration of the products. In the first

stage, i f the fatty acid and DETA are added together at the melting point of the fatty acid

(63 °C, palmitic acid) a spontaneous salt formation is observed as a gel with liberation of

heat. The salt/gel is rapidly overcome as the temperature is increased to ca 150 °C and is

not observed i f the reaction is carried out with the reagents preheated to cal50 **C. Salt

formation will also occur at room temperature. The second and third stages are

temperature-dependent. The lower temperature {ca 150 **C) mono/diamide formation stage

and at higher temperature and under vacuum {ca 240 **C, 30 mm Hg) or long reaction

times'^'"'^^'^ cyclisation to imidazoline. In monoamide formation, the reacting centres in

the salt are already in close proximity and the amide product can maintain a relatively

linear configuration. Therefore the inter-molecular bonding to be overcome to allow

elimination of a water molecule and amide bond formation is not too high. I f the fatty

acid/DETA ratio is 2:1, a diamide formation can occur. For cyclisation of the

mono/diamides to imidazolines, a much greater rearrangement of amides configuration is

required to allow the reacting centres to be positioned correctly and to allow subsequent

elimination of a second water molecule. Therefore there is a much higher energy

requirement to overcome inter-molecular bonding.

178

In contrast to the solid phase, when the reaction of fatty acid with DETA is carried out in

solvent (at suitable concentrations to ensure full solvation), the alkyi chain van der Waals

inter-molecular interactions are dispersed by much weaker solvent-molecule interactions

thereby eliminating steric effects. Thus a lower temperature is required to obtain the

correct molecular configurations for the reactions. Analysis of reaction sub-samples

(Chapter 4; Sections 4.3.4, 4.37 and 4.3.8) showed only small amounts of the amides

relative to imidazolines, even after only a short reaction time (1 hr). This indicates that due

to the low steric interactions, cyclisation of the amides is rapid and imidazolines are the

preferred products. Also, the ratio of acid to DETA, the order of addition of reagents (i.e.

DETA to acid or acid to DETA) and time over which reagents are added, may influence

final ratio of 1:1- and 2:1-imidazoline products. This is due to competition, and the relative

reactivity of the respective amine groups, of the DETA, monoamide and l:l-imida2oline

products for available acid.

Revised reaction schemes for solid phase and solvent based thermal reactions of fatty acids

with DETA based on the foregoing HPLC/ESI-MS experimental results are shown in

Figures 5.31 and 5.32. It is not known from this study whether the amides are primary,

secondary or secondary/primary amides. It is believed that the initial temperature, fatty

acid/DETA ratios and the method and time spans over which the reagents are mixed may

be the most important factors in determining the final ratio of products in both solid phase

and solvent based syntheses. An even more detailed study of these factors needs to be

carried out in order to arrive at more efficient syntheses of the desired products.

179

O H

Rapid exothermic amine salt formation

H

And/Or

H

0

.NH-

A 150°C

H2

.NH-

H,0 Alternate intermediates

And/Or

+ O H

A150 °C

0 ^ 1

.NH.

Via salt intermediate

H

0

H N s ^ R i And/Or

T HoN,

H

o

A 240 °C; -30 mm Hg

R

•NH.

R

NH

Figure 5.31 Proposed reaction mechanism for the solid phase thermal reaction of fatty

acids with DETA.

180

OH H

Very rapid formation of amine salt ^ 145 °C Refluxing xylene

And/Or 0 H3N. .NH-

- H p

r h :

H,

Alternate intermediates

Rapid - H,0 ntermediate

Compel

reaction + OH

Via salt intermediate

-H,0

T R

Figure 5.32 Proposed reaction mechanism for the solvent based thermal reaction of fatty

acids with DETA.

181

5.4 Conclusions

The thermal synthesis of 2:1-palmitic imidazoline proceeds via two different pathways depending on whether the reaction is carried out in the solid phase (Figure 5.31) or diluted in refluxing xylene solvent (Figure 5.32). The reaction products may be influenced by the method by which the reagents are added and the time span of their addition. Reaction intermediates and final products (1,1- and 2:l-palmitic imidazolines and mono and diamides) were identified and characterised by HPLC/ESI-MS and by MS°. CID MS° fragmentation pathways were determined for 1,1- and 2:l-palmitic imidazolines and 1,2-/1,3-paImitic and oleic diamides.

182

CHAPTER SIX

Conclusions and Future Work

This chapter summarises the conclusions from the results presented and discussed in

Chapters 2 - 5 . Proposals are suggested for work which would develop further the solid-

phase extraction (SPE), high performance liquid chromatography (HPLC) and ESI-MS°

methods used herein for the study of imidazoline-based and other oilfield chemicals. Such

developments would also aid further studies of the synthesis of imidazolines and related

amides by thermal reactions of fatty acids with diethylenetriamine (DETA).

83

6.1 Conclusions

The primary aim of this study was to investigate new analytical methods for monitoring the

environmental fate of the diverse polar organic chemicals used during the offshore

production of crude oils. Methods have been devised for the extraction, chromatographic

separation, detection and quantitation of some of these chemicals from environmental

matrixes. At the inception of the research, electrospray ionisation mass spectrometry (ESI-

MS) was an emerging technique that appeared to have attributes compatible with the

detection of some of these compounds. Use of quadrupole ion trap (QIT) mass

spectrometers for multi-stage mass spectrometry (MS", n = I - 10) seemed particularly

attractive. A range of speciality oilfield chemicals (corrosion inhibitors, scale inhibitors,

biocides and demulsifiers) were therefore investigated by ESI-MS°. Using appropriate

model compounds, compatible liquid chromatography (LC) methods and chromatographic

phases were developed for the extraction, separation and quantitation of speciality oilfield

chemicals from environmental matrixes. The developed methods were applied to the study

of real environmental samples as follows:

A range of speciality oilfield chemicals (corrosion inhibitors and demulsifiers; Chapter 2)

in which the identities of the active compounds were unknown, was examined by infusion

ES1-MS° (positive and negative ion) on a QIT instrument (LCQ™, ThermoFinnigan). Full

scan (MS) and collision induced dissociation (CID) multi-stage mass spectra (MS") were

obtained from the products. Analysis of spectra allowed identification of

alkylbenzenesulfonates, di-[alkyldimethylammonium-ethyl]elhers, alkylbenzyl-

dimethylammonium and imidazoline compounds. CID MS" fragmentation pathways were

determined for the compounds identified (Figures 2.2, 2.6, 2.8 and 2.10 respectively). The

184

identification of alkylbenzenesulfonates, alkylbenzyldimethylammonium cations and

imidazolines was confirmed by comparison of the mass spectral Segmentation pathways

with those of authentic compounds. The MS^ product ions for both the

alkylbenzenesulfonates (MS^ product ion m/z 119) and alkylbenzyl-dimethylammonium

cations (MS' product ion m/z 58) identified in the fiâgmentation pathways had not been

reported previously to the present author's knowledge. An authentic di-

[alkyldimethylammonium-ethyljether was not commercially available and ftiture studies

might include synthesis and co-chromatography of the compound.

Polar organic fi-actions (dichloromethane extracted) of real North Sea oilfield Produced

Water, were examined by infusion ESl-MS" (positive and negative ion).

Alkylbenzenesulfonates similar to those identified in the studied oilfield products were

observed in the Produced Water by negative ion MS and confirmed by MS°. The positive

ion mass spectra indicated the presence of diamides produced from hydrolysis of 2:1-

imidazoline corrosion inhibitor compounds and polyethoxylated compounds typical of

those used in conmiercial demulsifiers. The complexity of the spectra highlighted the

requirement for analytical separation of components prior to ESI-MS analysis in order to

more accurately identify individual components.

Examination of the oilfield chemicals and Produced Water extracts showed that ESI-MS"

was a powerful technique for identification and characterisation of polar chemicals. The

particular advantages of the ion trap multi-stage ESI-MS method were: the possibility of

both positive and negative ion detection (e.g. for quaternary amines and sulfonates

respectively); the ability through the so-called 'ZoomScan™' facility to determine the

accurate mass differences between ion pairs, thus allowing differentiation of the multiple

charge state of the ions and collision induced dissociation multi-stage mass spectrometry

which allowed fragmentation pathways to be studied, thereby allowing previously

185

unknown compounds to be identified and unambiguous identification by comparison with

authentic compounds.

Imidazoline compounds are widely used in speciality oilfield corrosion inhibitor products

and were shown in Chapter 2, to be amiable to ESl-MS detection and MS" characterisation.

As such, they were identified as suitable representative compounds for further

investigation by liquid chromatography (LC) coupled with ESI-MS and solid phase

extraction (SPE) methods for their determination in environmental matrixes.

In conjunction with a HPLC/ESI-MS method developed in a further part of the study

(Chapter 4, see below), a SPE method for the extraction of imidazoline compounds from

crude oils was developed (Chapter 3). A semi-quantitative but sensitive and specific

method, involving SPE with a silica phase, followed by HPLC/ESI-MS, was developed for

the determination of individual imidazolines at low (<10) parts per million concentrations

in crude oils. Whilst the method requires further optimisation due to the high experimental

losses of imidazolines during work-up, it nonetheless represents a considerable

improvement on previous techniques and should prove valuable for operational and

environmental studies of corrosion inhibitor and surfactant behaviour.

Pure authentic compounds were required to develop the SPE and HPLC methods and to

investigate the relative ESI-MS responses of imidazolines and amides for quantitation.

Therefore, syntheses of 1:1- and 2:l-palmitic and oleic acid derived imidazoline

compounds (Chapter 4) were carried out by solid-phase and solvent-based thermal

reactions of diethylenetriamine (DETA) with palmitic and oleic acids. Although a simple

synthesis and purification method for pure compounds was not optimised, reaction sub-

samples and products were successftilly used to develop a high performance liquid

186

chromatography (HPLC) separation with coupled ESI-MS detection (Chapter 4) and a SPE

of 2:1-palmitic and oleic acid-derived imidazoline from crude oil (Chapter 3).

A poly(styrene-divinylben2ene) HPLC phase (Chapter 4) in conjunction with a gradient

elution method using trifluoroacetic acid (TFA) ion-pair reagent with modified methanol

(or ethanol) and water eluents, was determined to be the optimum for analytical separation

with ESI-MS detection of palmitic and oleic acid-derived 2:1-imidazolines, 1:1-

imidazolines, monoamide and diamide compounds (Chapter 4; compound structures are

given in Chapter 3, Figure 3.1). The HPLC/ESI-MS responses of palmitic and oleic 2:1-

imidazolines (2:1-PI and 2:1-01 respectively) were investigated and detection limits of

0.0lug mL'' 2-1-PI and 01 standard (signal/noise > 3) were determined in the full scan

range m/z 100 - 1000. These concentrations are much lower than those previously

published for imidazolines (50ng mL"' and 150 ng mL" ' ) . " '^ The HPLC/ESI-MS method

was used to separate the imidazoline and amide components of a commercial imidazoline

product (Chapter 4). The presence and separation of a range 1:1- and 2:1-imidazolines and

the corresponding monoamides and diamides derived from Cig acids with up to three

degrees of unsaturation (Ci8:o, Ci8:i, Ci8:2 and Ci8:3) ^nd C20 acids with up to three degrees

of unsaturation (Cioo, C20:i» C20:2 and C20:3)- Separation of structural isomers of the

compounds was also shown.

When syntheses of model imidazoline compounds by thermal reaction of DETA with fatty

acids were carried out (Chapter 4). it became apparent that the developing HPLC/ESI-MS

method was a powerful technique for the study of this important reaction. Analyses of

reaction sub-samples and products highlighted the contradictory results in the published

literature and specifically the existence of l:l-imidazoline and monoamide intermediates

was shown. Due to the requirement for efficient syntheses of high purity model compounds

187

an investigation of solid-phase and solvent-based thermal reaction of DETA with palmitic

acid was carried out (Chapter 5), It was shown that the thermal synthesis of 2:1-palmitic

imidazoline proceeds via two different pathways depending on whether the reaction is

carried out in the solid phase (Figure 5.31) or diluted in refluxing xylene solvent (Figure

5.32). Reaction intermediates and fina] products (1:1- and 2:l-palmitic imidazolines and

mono and diamides) were identified and characterised by HPLC/ESI-MS and by MS°. CID

MS" fragmentation pathways were determined for 1:1- and 2:1-palmitic imidazolines and

l,2-/l,3-palmitic and oleic diamides.

6.2 Future work

The use and discharge of chemicals used in the United Kingdom offshore oil and gas

industry (The Offshore Chemical Regulations 2002)'" have recently changed from a

voluntary scheme (the Oslo Paris Commission (OSPAR) Harmonised Offshore Chemicals

Notification Format (HOCNF)) to compulsory regulation (OSPAR Harmonised

Mandatory Control Scheme (HMCS)). The scheme requires chemicals to be ranked by a

Hazard Quotient (HQ: predicted environmental concentration/predicted no effect

concentration (PEC/P^fEC ratio)) determined by chemical hazard assessment and risk

management models (e.g. CHARM) based on the toxicity, bioaccumulation potential and

biodegradability of each chemical. Such mathematical computer models predict the

environmental concentrations/discharges based on theoretical calculations (e.g. CHARM)

or at best, based on laboratory and some field studies for a limited range of chemicals (e.g.

PROTEUS'^^). A major problem for real predictions and assessments of these chemicals

has been the lack of suitable analytical techniques. However, new methods such as those

described in this thesis may allow the detailed characterisation of oilfield chemicals and

188

determination of their fates in the marine environment and 'sea-truthing' of the data

currently used by mathematical models such as CHARM and PROTEUS. This is

important as it has been shown that oilfield discharges (e.g. Produced Water) can produce

undesirable biological impacts on marine organisms'*** '' ' **" * * and large amounts

(estimated 313,790 tonnes of oilfield chemicals used and 106,592 tonnes discharged) of

oilfield chemicals were used and discharged by the UK sector in 2000.^' The requirement

for better analytical techniques to allow investigation of oilfield chemicals is expected to

increase. Thus, improvements to developed methods such as those described in this thesis

may ftirther advance the study of these and similar chemicals.

The HPLC separation of imidazoline and amide compounds developed could be improved

by changing the column used in this study (PRP-1, 5 n, 4.1 x 50 mm; Hamilton) to a more

efficient 3^ PRP-1 phase with a change in column dimensions (2.1 x 100 mm). Decreasing

the internal diameter (ft-om 4.1 to 2.1mm) allows the use of 150 - 200 ^L min"' (c/: lOOOuL

min"') flow rates which do not require splitting prior to the ESI source. This alleviates peak

broadening due to the couplings required for splitting the post column eluent flow and

allows the entire sample injected on column to enter the ESI source. The advantages of this

change have been shown in a separate study by the present author*^^ for siderophore

compounds (iron complexed and non-complexed rodotoluate, ferrioximine and

ferrichrome) in a modification of the developed HPLC/ESI-MS method. The use of inert

polyetheretherketone (PEEK) columns in place of stainless steel columns may also

improve peak broadening and resolution as imidazolines have a high surface activity with

iron. Indeed, the stainless steel tubing and components of the auto-sample used in the

present study could be substituted with a metal free sample injector system. Further

investigations of ion-pair reagents and eluent modifiers (such as pentafluoropropionic acid)

may improve separations. Improved resolution of the l-/2-monoamides and 1,2-/1,3-

189

diamides would allow HPLC/ESl-MS identification MS" characterisation of these isomers

in reaction intermediates, products and environmental samples.

A more detailed study of the solid-phase and solvent-based thermal reaction of DETA with

fatty acid could be carried out with HPLC/ESI-MS, ESI-MS° and other spectrometric

methods of analysis. An emphasis on the important initial method of addition, time span,

temperature and concentration of reagents may provide a better understanding and method

for efficient synthesis of desired products, for what is still a debatable reaction.

The SPE method developed requires further development to improve the efficiency of

imidazoline extraction from crude oils. Specifically the loss of sample by sorption to

surfaces during sample handling procedures requires investigation. Comparisons with other

solid phase supports (such as DIOL, CN and NH2) which are less sensitive to effects of

water wet oils may be more efficient. The high organic content required to elute

imidazolines and amides from the poly(styrene-divinylbenzene) HPLC phase suggests that

the phase may be suitable for solid phase extraction of these compounds from

environmental waters such as oilfield Produced Water and marine samples.

The specific identity of several ethoxylated compounds observed by ESI-MS in oilfield

products (Chapter 2) was not established during this study due to the limited information

on the product composition and the limited time available. Further studies of these specific

products are required to establish their identities and subsequently their extraction,

chromatographic separation from and quantitation in environmental matrixes.

ESI has been shown to be suitable for the detection of some polar compounds in oilfield

chemicals however; it may not be applicable to many other compounds or be the most

sensitive method of detection. Atmospheric pressure chemical ionisation (APCI) and 190

atmospheric pressure photoionisation (APPI; an emerging ionisation process for interface

with liquid chromatography/mass spectrometry*'**'* ') may be more appropriate for other

compounds of interest in oilfield products. A study comparing ESI, APCI and APPI

detection for compounds in oilfield chemicals would enable the most appropriate method

for each compound or group of compounds to be determined A comparison of ionisation

interfaces would be greatly enhanced i f the separate ionisation interfaces were combined

into one interface. Currently, interfaces that allow sofhvare switching from ESI to

^ ^ j i 3 2 . i 3 3 ^ .^^ ^^^^^^ APPl' '° are becoming commercially available.

However there does not appear to be reports of dual ESI/APPI or triple ESI/APCI/APPI

interfaces. The combination of ESI and APPI as a single mass spectrometer interface could

be a very powerful detection system for highly polar and non-polar compounds in a single

chromatographic separation. A study to investigate the feasibility of a combined ESI/APPI

could be carried out.

191

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210

APPENDIX

211

0.45

0.40

0.35

0.30

0.20

0.15

0.10

0.05

U l Xv uio)

, o O -xj

R and R,

2:1-Palmitic Imidazoline 2 ([2-(2-Hexadecyl-4,5-dihydro-1H-imida20l-1-yl)ethyI]hexadecyIamide)

3 4000 ' i l l ' ' " " 3500 3CdO 2500 2000

Wavenumber (cm-1) ' I 1500 1000 500

Figure A . l Fourier transform infrared spectrum of 2:1-palmitic imidazoline synthesised

by thermal reaction of palmitic acid with diethylenetriamine refluxed in

xylene solvent (Chapter 4; Section 4.2.5.3): (Wcm"'); 1643, 1550 (-NH-

C O ) , 1608 (C=N).

212

100 ^

90

80

8 70 CD

I 60

I 5 0 ^

I 40 a.

30 d

20--

0

100

50 -i

632.6 1

630.6

633.6

| " " l " " T ' ' " r ' " | - ' ' " l " " l ' "

634.6

630 635

308.4 325.3

632.6

630J

633.5

648.6 l ' ' ' | " M " ' l ' ' ' l ' ' N ' ' ' | " ' l ' ' ' | i ' M ' ' M ' ' ' | ' ^ 4 i ' M ' ^ ' M ' ' M ' ' i | i ' ' l ' i i | " ' i i " l ' ' ' | ' ' ' i ' ' ' i ' ' ' l " ' | i ' i | ' ' ' h ' ' ' l " i | ' i ' | i ' ' |

100 200 300 400 m/z

500 600 700

Figure A.2 Infusion ESI-MS mass spectrum of oleic-diamide product (Chapter 4,

section 4.3.8). Positive ion full scan spectra: (auto-tuned on ion m/z 632.6,

m/z 50 - 700, capillary voltage (+16.03 V), l " octapole (-3.15 V), 2nd

octapole (-6.44 V) and tube lens (-21.17 V). Inset is the ZoomScan of ion

m/z 622.6.

213

100

90

80

J 60 < I 50 CO

I 40

30

20

10

0

615.5

308.3

306.3.

614.6_

325.2

350.4 l ' " | " ' l " ' ] " M " ' l " ' | " ' | l " l ' l ' l ' ' ' M ' " | " i | ' " l

^8.4 436.4 495.9 553.7 632.5 L | " ' | i " l " ' l " ' l " ' | " ' l " ' l " ' l " M " ' |

200 300 400 500 600 700 m/z

Figure A.3 ESI-MS^ CID mass spectrum of the oleic-diamide precursor ion, m/z 632.6

(39 % AA) in the fiill-scan spectrum (Figure A.2).

214

100-1

50 i

308.3

r " | I 200 < 1

A

351.4 586.1 " • I I " I I " 1 ' " I" ' I ' I' -M I' I • I ' • I I • • • • I

300 400 500

615.5 X

^ 100 98

50 i

600 700

B

MS'

112.1 126.0 210.2^224.0 264.3

100 *(yL l!i!Vii>ii..'>|i<i.fHiw!li .Mti" ii''4iL''l">i>"'

308.4

150 200 I I I I I I I I I I | 1 [ I I | l 1 I l | I I I I J I I I I j r T T r [ T T I 1 | T I I I |

250 m/z

300 350 400

Figure A.4 ESI-MS° mass spectra of the oleic-diamide MS^ product ion {m/z 615.6) in

the MS^ spectrum Figure A.3. (A) MS'' on precursor ion m/z 6.15.6 (36 %

AA), (B) MS" on product ion m/z 308.3 (43 % AA).

8 100^ % C € 5 0 i

308.3

30X3.

MS-

325.6 i |nN| i in |Hi i | i i i i | i i i .p i i i | in i | i i i . | iN . | .LM | i i i i | i i i i | in i |nn| i i i , | i . i i | i i i i | i i i i |nn| i i i i | i i i i |M .V | .n i |n i i | i . i i | i i i i [ i i i i |H

100 150 200 250 m/z

300 350 400

Figure A.5 ESI-MS mass spectrum of the product ion {m/z 325.2; AA 29 %) in the

oleic-diamide MS^ spectrum of product ion (w/z 615 .6) in the MS^ spectrum

Figure A.3. MS" on the m/z 308.3 product ion is identical to Figure A.4B.

215

100-1

8 50 c CO c 3

307.4

179.1 3 0 5 . 3

MS-

P-^_35.1.1 614.6 i ' " r " i " ' i " ' i " ' i ' " [ " M " M ' " i i " i " ' | i " i " i i " i i " ' i " ' i " ' i ' " i " ' i " ' j ' " | i " i " i i " ' i ' " i " ' i

200 300 400 500 600 700

5 100

50 i

97.2

MS'

| i I n J 1 1 I I j 1111j i : 111

100

111.0 153.3 ^9^.4 235.3 279.4 307.6

r- ' y \ 1 1 I I 11 I I 1111 I I I I I IIITTTT ^•1"" 150 200 250

m/z

| i i M | i i M [ m m i i i [ i i i i | r M H i i i r | T T i H T n i | T r T T ] T ; i r |

300 350 400

Figure A.6 ESI-MS" mass spectra of the oleic-diamide MS^ product ion {m/z 614.6) in

the MS^ spectrum Figure A.3. (A) MS' on precursor ion m/z 6.14.6 (41 %

AA), (B) MS" on product ion m/z 307.4 (51 % AA).

216

1.00 i

0 95

085

0 80

0 75

1,3-Oleic diamide

b c b d H

0-70jH3C(H2C)7{HC)2(H2C )rY^ o

e g g H d t ) c b a

^ N ^ " ^ ^ Y ^ ( ^ " 2 ) 6 ( C H ) 2 ( C H 2 ) 7 C H 3

065

060

055

o:5oi

0A5j

040

oasi

030

0:25

0:20

0J5J

o i o i

0 05

0

e

200

7 6

r : 4 00

f

395 391 7.87 4.1541.53 8.72

4 ppm

Figure A.7 H NMR spectrum of the 1,3-oIeic diamide product -diamide formed from

hydrolysis (during storage) of 2:1-oleic imidazohne (Chapter 4, section

4.3.8). CDCI^, 270 MHz.

217

0.45

040

qW

030"

8 0 ^ I

i 020" 0.15

0.10

0.05

4000 3500 3000 aOO 2000 Wavenumber (cm-1)

1500 1 0 0 0 b o o ' ' '

Figure A.8 Fourier transform infrared spectrum of the crude 2:l-palmitic imidazoline

product of thermal reaction of palmitic acid with DETA in xylene solvent

(Chapter 5; Section 5.2.4): (u/cm"'); 1645. 1550 (-NH-C=0), 1608 (C=N).

218

0.40

0.36

0.30

0.25

0.20 i •

0.15

0.10

0.06

— IXJ ro fo cji ,n ^ e^t

K g

'•| ' ' T •'-T 4000 3500 3000 2500 2000

Wavenumber (ctv 1) 1500

• I • 1000

• I ' 500

Figure A.9 Fourier transform infrared spectrum of the recrystallised 2:1-palmitic

imidazoline product of thermal reaction of palmitic acid with DETA in

xylene solvent (Chapter 5; Section 5.2.4): (v/cm ' ) ; 1639, 1552 (-NH-C=0),

1606 (C=N).

219

0.45 A

en to

0.30 :1

I S

4000 3500 3000 2500 2000 Wavenumber (cm-1)

1500 1000

Figure A.IO Fourier transform infrared spectrum of the crude palmitic-diamide product

of solid phase thermal reaction of palmitic acid with DETA (Chapter 5;

Section 5.2.5): (Wcm"'); 1639, 1562 (-NH-CO).

220

0.56

0.50

0.45

0.40

0.35

5 0.30 E

0 .^

0.20

0.15

0.10

0.05

- t - T T -4000

1 ^ 1 \ CD 1 1 u> 1 ^

M to a> 09 CO

CD

00 ro CD (o u to P

w - to to o>

ro

' I I ' ' 2500 2000

Wavenumbcr (cnvl)

I • I ' 3500 3000 1500 1000 500

Figure A. ] 1 Fourier transform infrared spectrum of the recrystallised palmitic-diamide

product of solid phase thermal reaction of palmitic acid with DETA

(Chapter 5; Section 5.2.5): (u/cm'*); 1639. 1566 (-NH-C=0).

221

0.45

0.40

0.35

0.30

§ 0 2

0.20

0.15

0.10

0.05

to w

' I I ' ' 2500 2000

Wavenumber (cm-1) 4000 3500 3000 1500 1000

Figure A.12 Fourier transform infrared spectrum of the recrystallised 2:l-palmitic

imidazoline product of solid phase thermal reaction of palmitic acid with

DETA (Chapter 5; Section 5.2.5): (Wcm"'); 1643, 1550 (-NH-C=0), 1608

(C=N).

222

022

021

0 20

019

o le i

o l e i

014

013

0.12

0.11

0.10

009

008

0 07

0 06

0.05

0 04

0 02

001

8

2:1-Palmitic imidazoline

h g

J c ^ H3C(H2C) i2

a b

1.00

' I ' ' ' M ' ' • • I ' ' ' ' I

b a (CH2)i3CH3

d

4.58 6.21 0 15 4.50 4.4759.33 7 76

4 ppm

' ' ' ' ' I 3

Figure A.13 ' H N M R spectrum of the 2:1-Palmitic imidazoline product the solid phase

synthesis (Section 5.2.5). CDCb, 270 MHz.

223

Tool

0 90

0 85

Ool

070

060

055

050

0 45

0 40

0.35 :

0 30

025

020

0.15

010

005

1.3-Palmitic diamide

d d a b c H f f H c b a

0 H g

CO

e CD

00 ^ o CD

lO CO ^ CO CO CO CO CO CO (Nj CO CO

CNCN CN CM

CD O O

1.49 3 80 4.00 3.74 8 83 49 15 6 36

' ' I ' 4

ppm 2 1

Figure A.14 H NMR spectrum of the 1,3-Palmitic diamide product of solid phase

synthesis (Section 5.2.5). C D C I 3 , 270 MHz

224

T ^ S E A R C H & D E V E L O P M E N T AstraZeneca Global Safety. Health & Environment Department

Number 100 - September 2002

Analysis of Highly Polar L o w Molecular Weight Organic Molecules: Part 1 - HPLC Separation using a Novel Hypercrosslinked Resin

Background The aim of this industry sponsored PhD project was to research new approaches to the problem of pre-concentration, separation and identification of polar or ionisable organic molecules from aqueous media.

The practical work, which has now been completed, was divided into two. areas of study: The investigation of novel materials for the isolation and separation of model coippounds, and the use of multi-stage mass spectrometry techniques to provide both molecular weight and specific structural information for the identification of unknowns in complex mixtures.

Examples of the latter are described in a second R&D bulletin (Ref 101).

The development of HPLC methods involving reverse phase silica gel columns was a major ^

(j> advance in solving the difficult problem of separating polar organic molecules with high efficiency. However, many low molecular weight highly polar molecules, are still difficult to separate on commonly available phases such as octadecyl (CI8) bonded silica, even in highly aqueous mobile phases. One reason for this is the relatively weak hydrophobic interaction between the polar molecule and the C18 bonded layer, dihydroxybenzenes, (Figure 1, compounds 2, 4 and 5) being a typical example, producing very short retention times.

Polymeric phases, based on neutral polystryrene resins, have been investigated as altemative reverse phase substrates to bonded silica gels for polar molecule separations.

Although in some cases there has been an improvement in separations, many o f these polymeric phases give asymmetrical peak shapes with poor resolution. Nonetheless, a recent development involving hypercrosslinked polystyrene resins appears to have overcome this problem and shows great potential for the efficient separation of highly polar compounds.

Normally, a high degree of crosslinking would make a dense non-porous substrate with poor separating capabilities.

However, a special polymerisation process, first pioneered in Russia, produces highly porous

particles even when the degree of crosslinking approaches 100%.

A research collaboration with Moscow University provided a number of novel phases for investigation. One of these phases, a hypercrosslinked resin called MN200 (originally used for the large scale treatment of waste waters containing polar compounds), was found to have an unusually strong affinity for a range of highly polar phenolic compounds. The use of this phase with an LCMS-compatible water/methanol mobile phase provided very promising high efficiency separations without the usual requirement for inorganic buffers.

Separation of phenols using MN200 column An example of the isocratic separation of eight phenolic compounds is shown in Figure 1. These

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compounds are usually poorly retained and therefore difficult to resolve by conventional reverse phase LC.

The separation is exceptional in that good retention and resolution was obtained with a high degree of symmetry in peak shape, using a short column (100 mm). The separation was achieved with high percentages o f methanol, which is beneficial to LC-MS sensitivity, a technique of major importance for identifying unknown polar compounds in environmental water samples.

Gradient elution could be used to decrease the retention time and peak width of the later eluting peaks (6-8) and may be considered to separate much more complex mixtures of polar compounds.

One of these materials, the hypercrosslinked resin MN200, was found to have an unusually strong affinity for highly polar phenolic compounds and provided an improved separation when compared to existing methods. The use of MN200 as a SPE packing material for the extraction o f polar organics from aqueous samples should be evaluated in a future project.

Additionally, because polar compounds are highly retained when using a mainly aqueous mobile phase, the MN200 should be ideally suited for use as a solid phase extraction (SPE) packing material for the extraction/concentration of polar organics from aqueous samples.

Figure 1. The separation of eight phenolic compounds using a 5 i im MN200 (100 x 2.1 mm) column at a flow rate of 0.15 ml min '

20 25 30 35 Minutes

40 45 50

Conclusion Ilollaboration with the Moscow University illowed the evaluation of novel LC packings, >reviously unavailable in Europe. One of these naterials, the hypercrosslinked resin MN200, was bund to have an unusually strong affinity for lighly polar phenolic compounds and provided an mproved separation when compared to existing nethods. The use of MN200 as a SPE packing

material for the extraction of polar organics from aqueous samples should be evaluated in a future project.

This bulletin was prepared by Malcolm Hetheridge, Paul McCormack', Phil Jones' and

' University of Prof. Pavel Nestorenko^ Plymouth and ^ Moscow University as part of the AstraZcneca Global SHE Research & Development Programme

aZcnco. Global SalelyHeo»h&EnvironmenlDepamnen. Bnôm Devon T Q S e B A UK Te. ^44 1603 682862 wcbsi.o fl.oba..she.astr3zeneca.not

R E S E A R C H & D E V E L O P M E N T AstraZeneca^ Global Safety, Health & Environment Department

Number 101 - Sqjtcmber 2002

Analysis of Highly Polar L o w Molecular Weight Organic Molecules: Part 2 - New Methods for the Identification of Polar Chemicals in

Complex Mixtures

INTRODUCTION The use of liquid chromatography-mass spectrometry (LC-MS) has increased in importance over recent times. Unfortunately though, LC-MS spectra often only provide the molecular weight of an unknown chemical and reveal little structural information. Methods such as LC-MS-MS are more powerful and in our studies we have employed the latest multistage MS techniques.

Multiple stage mass spectrometry (MS") with both positive and negative ion detection allows high speciScity detection and characterisation o f a wide range of polar and charged molecules. For example, linear alkylbenzenesulfonates (LAS), alkyldimethylbenzylammonium compounds, ' the previously poorly characterised corrosion inhibitors, 2-alkylimidazolines and a series of di-[alkyldimelhylainmonium-ethyl]ethers, were all identified and characterised in commercial formulations and/or marine 'produced* waters (Ref 1 and 2). The technique wi l l benefit the future study of environmental fate and effects of these and

b similar polar compounds. xP"

EXAMPLES Two features of the LC-MS analysis: zoom scan and MS" are illustrated here:

A positive ESI full scan mass spectrum of a sample containing alkyl di-quatemary salt, showed two distinctive odd m/z ion series. Figure L The ions in the most intense series, centred on m/z 249, differed fix)m each other by m/z 14, whilst those in the series around m/z 533 differed by m/z 28. The charge state of ions in each series were elucidated by the use of the so-called 'ZoomScan*. This allows resolution of isotope peaks for up to +4 charge-state ions. Thus, ions in the first series eg m/z 249.4 showed mass differences of 0.5 Da (Fig. IB) indicating these to be doubly charged ions (M^V2). By contrast, analysis of the higher mass ion series eg m/z 533.4 showed a mass differences of 1.0 Da (Figure. IC) consistent with singly charged ions (M^/1). This quickly allowed the molecular weight of these compounds to be determined. Structures were subsequently identified by LC-MS" analysis.

<P

Figure L Mass Spectrum and 'Zoom Scan' Spectra of quaternary amine salts

249.4

483.5

214.3

645.6

m B35.7

b)

249.9

A 2?P-3

. I L L U L . .

534.35353

200 400 600 BOO

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Figure 2. MS° spectra and Fragmentation pathways for Imidazoline analogues

3 307J

1

i

1

•i

•

b ) too 00

80

• TO •!

s so

I so

20 -a to I 0

4 97.0

100 150 200 250 300 5M 400 <50 500

(1) H N T ^ ^ ^

nVz 350.7 R1 = C ^ H j ,

r - i \ ° '

J R1

Loss of

2-AIKyl-1 -ethytamine-2-imidazoIine

3 307J

t i io

Loss of

25tJ 305J

200 250 mft

( 3 )

HN^NH

- f — ^ Lossof R1 AIXylgrcM)

mfe 307.2

(4)

HN<^NH

mft97.0

R2 = C ^

The LC-MS" capability is illustrated by the characterisation of the highly polar, "sticky", 2-alkylimidazoline corrosion inhibitors (Figure 2), identified in formulated product and in environmental samples.

The molecular ion, in this example m/z 350, is fragmented to ra/z 307 (Figure 2a) by loss of ethenamine (43 Da). The fragment ion, m/z 307 is then isolated and fragmented to give further structural information eg loss of alkyl side chain. Figure 2b. In this way, a fragmentation pathway can be developed (Figure 2c), to allow a firm identification to be made.

Few other techniques provide this level of information for complex mixtures of polar chemicals at sub parts per million concentrations, and therefore the LC-MS" method promises to be a boon to analytical chemists for the characterisation of many polar chemicals.

Conclusion An additional benefit from this study was the considerable expertise gained in the interpretation of sequential fragmentation patterns provided by the MS" technique. The development of this particular MSMS expertise at Plymouth University, will provide an invaluable foundation for future collaborative projects.

References

1 McCormack et al (2001). Wat. Res. 35 (15) .3567-3578.

2 McCormack et al (2002). Rapid com. mass spec 16, 705-712.

This bulletin was prepared by Malcolm Hetheridge, Paul McCormack* and Prof. Steve Rowland ' University of Plymouth as part of the AstraZcncca Global SHE Research & Development Programme.

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R A H D C O M M U N I C A T I O N S IN MASS S P E C T R O M E T R Y Rapid Canwiun. Mas? Spectrom. 2002; 16: 705-712 Publishfjd online 18 February 2002 in Wiley InterScience (www.interscicncc.wilcy.com). DOI: 10.1002/rcm.625

Liquid chromatography/electrospray ionisation mass spectrometric investigations of imidazoline corrosion inhibitors in crude oils

p. McCormack, P, Jones and S . J . Rowland* Petroleum and Environmental Geochemistry Group. Department of Environmental Sciences, Plymouth Environmental Research Centre. University ol Plymouth. Drake Qrcus, Plymouth PL4 8AA. UK

Received 28 October 2001; Revised 25 January 2002; Accepted 25 January 2002

The so-called imidazol ines (2 -a lky l - l - [e thy la lkyIamide] -2 - imidazo l ines and 2-a lky l - l -e thyIamine-2-imidazo l ines ) are a g r o u p o f surface-active compounds, complex mix tures o f w h i c h are used by various indus t r ies as surfactants a n d corrosion inh ib i to r s . A l t h o u g h the i r i n d u s t r i a l synthesis was reported over 100 years ago, f e w methods f o r the de te rmina t ion o f i n d i v i d u a l imidazol ines i n mixtures , i n c l u d i n g i ndus t r i a l matrices such as crude oi ls , have been repor ted . Here w e demonstrate that s p i k i n g o f crude o i l s w i t h synthet ic imidazol ines f o l l o w e d b y sol id-phase extraction and l i q u i d chromatography/electrospray ion i sa t ion multistage mass spectrometry (LCyESI - MS" ) a l l ows an es t imat ion o f l o w (<10) parts per m i l l i o n concentrations o f i n d i v i d u a l im idazo l ine s i n crude oi ls . W h i l s t non-op t imised at present, the method is a s ign i f ican t advance and may prove usefu l not o n l y f o r i m p r o v i n g an unders tanding o f the mechanisms o f indus t r i a l i m i d a z o l i n e synthesis a n d f o r m o n i t o r i n g d o w n h o l e and topside o i l f i e l d operations, but also f o r the d e t e r m i n a t i o n of the fate o f imidazol ine-based o i l f i e l d corrosion inh ib i to r s and surfactants i n the env i ronment . C o p j T i g h t © 2002 John W i l e y & Sons, L td .

The advent of electrospray ionisation mass spectrometr)' (ESI-N4S) has seen application of the technique to the identification of a growing number of polar chemicals in environmental and industrial matrices^"* Coupled w i t h l iquid chromatography (LC), ESI-MS has been used for Ihe determination of chemicals as diverse as positively charged quaternary benzalkonium chlorides ('Quats') and anions of linear alkylbenzene sulphonates ( 'LAS'). For example, Gough and Langley"* demonstrated application of LC/ESI-MS techniques to the detection of a variety of polar organics in oi lf ield chemical formulatior^ and oi l f ie ld produced water (PW) including Quats (used as biocides) and corrosion inhibitors such as the so-called imidazolines (2-alkyl-l-[ethylalkylamideJ-2-imidazolines (e.g. \, III) and 2-alkyl-l-ethylamine-2-imidazoIines (II)). Used wi th multistage ion trap MS (MS"), we were able to employ electrospray ionisation, not only in the detection of Quats, LAS and imidazolines in o i l f ie ld chemicals and PW, but were also able to assign unknowns such as a di(aJkyldirnethylammonium ethyl) ether in the mixtures by elucidation of the MS fragmentation pathways in up to five MS steps* (viz: ESI-MS^ . Clearly, ESI-MS" has great potential for the determination of numerous chemicals which were previously outside the analytical w i n d o w of most methods.

* Correspondence to: S. J. Rowland, Petroleum and Environmental Geochemistry Group, Department of Environmental Sciences, Plymouth Environmental Research Centre, University of Plv-mouth Drake Circus, Plymouth PL4 8AA, UK. E-mail: [email protected]

However, although detection of oilfield chemicals has been reported, few authors have reported ESI-MS methods for the quantitation of polars such as imidazolines;'^'^ and there are no reports of their determiriation in complex industrial matrices such as crude o i l . For imidazolines this is important for the assessment of the efficiency of both downhole inhibi tor addit ion (so-called squeezing)^ and to topside operations where control of dosing rates for the protection of metalwork reduces over-dosing and consequent economic and environmental costs. Whilst methods such as thin-layer chromatography have been used previously to detect imidazolines in crude oils,^ such methods at best only allow total imidazolines to be determined.

In the present study we report the use of multistage L C / ESI-MS for the identification and estimation of individual imidazolines i n crude oils. We have synthesised individual imidazolines and used these to dose crude oil at known concentrations to try to measure the efficiency of the recovery of the compounds by solid-phase extraction (SPE) methods and to calibrate the LC/ESI-MS responses of the individual compounds.

MATERIALS AND M E T H O D S

Chemicals Ultrapure water was obtained f r o m an Elgastat filtration system (Elga, H igh Wycombe, UK). A l l solvents used were HPLC grade except glass-distilled diethyl ether (ether; Ralhburn Walkerburn, UK and BDH, Poole, UK). Hypcr-

Copyright r 2002 John Wiley & Sms. Ltil.

706 P. McCormack, P. joncs and S. J. Rowland

REACTANTS

RCIVI

R C O j H + HjN

Fatty Acid DETA

irfTERMEDIATES & PRODUCTS

H RCO — N'

IV Monoamide

R C O — N NCOR

V 1.3Diamide

COR

VI 1,2Diamide

NCOR

' R^'^-CtsHj, III R=/i-C,7H33 "2:1 imidazolines"

N . O . N N H .

II "1:1 imidazolines"

solv-grade methanol (MeOH), propan-2-ol (IPA), ammonia (0.88), trifluoroacetic acid (TFA) and xylene (sodium-dried) were f rom BDH. Dichloromethane p C M ) , ethanol (EtOH). hexane. acetone and toluene were f r o m Rathbum. Sodium acetate (AcNa, 99%) was Aristar grade f rom B D H . Diethy-lenetriamine (DETA, 98.5%) was supplied by ACROS Organics, Ltd, (Goel, Belgium) and palmitic and oleic acids (90%) were f rom Aldr ich Chemical Company Inc., ( M i l w a u kee, W I , USA).

The crude oils were Middle Eastern crudes. The corrosion inhibitor active ingredients were f r o m a commercial supplier.

Synthesis of 2-aIkyl-l-[ethyIalkyIamide]-2-imidazolines 2-Pentadecyl-l-|N-ethylhexadecylamidel-2-imidazoline(2;l-Pl; I) and 2-heptadecenyl-l-(N-€thyloctadecenylamide]-2-imidazoline (2: l-OI; III) were synthesised by both solid-phase and solvent-based reactions f r o m palmitic and oleic acids and DETA by previously published methods.*"^ Stock solutions were prepared in McOH and diluted as required. Calibration solutions were prepared by serial d i lu t ion .

Solid phase extraction (SPE) Imidazolines were isolated f rom hexane or f rom crude oils (1 g) dissolved in hexane (1 mL) by use of an Isolute vacuum manifold and Isolute Si SPE cartridges (1 g x 6 mL). Briefly the procedure was: hexane preconditioning, sample loading, hexane elution, ether e lu t ioa vacuum drying (few seconds), imidazoline elution w i t h IPA/anunonia {cf. Kef. 8). Imidazoline fractions were b lown to dryness (nitrogen), reconstituted to 1 m L and transferred to 2-mL glass autosampler vials via a 1-mL glass syringe and expelled through a 0.2-|im PVDF syringe filter.

High performance liquid chromatography (LC) LC was carried out using a P580A binary pump (Dion-ex-Softron GmbH, Germering, Germany) wi th 1 m L m l n ~ ' flow rate, split '>-200jiL high pressure micro-splitter valve (UpchurCh Scienrific Ltd , Oak Harbor, W A , USA) to the mass spectrometer and the residue to a UV6000LP diode array detector (Thermoquest, San ]ose, CA, USA). 20-pL sample injections were made w i t h an ASI 100 autosampler (Dionex-Softron G m b H , Germering, Germany). A gradient elution was carried out as described previously using modified MeOH and water solvent and a 5-|jm, 50 x 4.6 nun reverse phase column.^

Mass spectrometry (MS) Mass spectrometry was carried out using a ThermoQuest Finnigan Mat LCQ (San Jose, CA, USA) ion trap mass spectrometer fitted w i t h an electrospray interface. Data were acquired and processed w i t h Xcalibur 1.0 software. Instrument tuning and mass calibration was carried out and checked using the automatic calibration procedure ( tuning and calibration solutions caffeine (Sigma, St. Louis, M O , USA), MRFA (Finnigan Mat, San Jose, CA, USA) and Ultramark 1621 (Lancaster Synthesis Inc., Widham, N H , USA) in methanol/water/acetic acid (50:50:1, v / v / v ) ) . Instrument method oprimisation was carried out by infusing I M sodium acetate at I j i L min~^ into a 200 | i L min"^ eluent f low from the LC system by way of the built-in syringe pump, a Hamilton 1725N (250 \iL) syringe (Reno, CA, USA) and a PEEK Tee union (Upchurch Scientific Ltd, Oak Harbor, W A , USA). The automatic tune function was used on a suitable sodium trifluoroacetate adduct ion. For the positive ion f u l l scan range m/z [100-1000] tuned on adduct ion m/z 563 the fol lowing instrument parameters were used: source voltage, +4.5 kV; capil iaiy voltage +20V; tube lens offset, -MO.OOV; capillary temperature, 220°C; rutrogen sheath gas f low rate, 60 (arbitrary units) and nitrogen auxiliary gas 20 (arbitrary units).

RESULTS AND DISCUSSION

Synthesis of 2-alkyI-l-[ethyIaIkylamideJ-2-imidazolines Ever since the initial synthesis of 'imidazolines' described by H o f m a n n " in 1888, there has been debate concerning the mechanism of the reaction between fatty acids and tria-mines.''^" ' ^ ' ^ Indeed, even the existence of the compounds has been questioned.'^ Yet the subject is of major importance to the efficient deployment of anti-corrosion measures since

Cnpyrighl r 2002 Jnhn VVik-y & Stms. Ltd. Rnfiil Coiiiniini. Mai^s SfWlnm. 2002; 16: 705-712

R C M L C / I E S I - M S to detect imidazolines in crude oils 707

KU:1.36E7

r . V + \a

m/z 562.5

50 m/z5S0

-s too q

so

V + VI j]^ M L - 2 ^ 5

c

m/z 324.4 NU 4.71E6

d

m/z 342.4 ML: !.71E5

e "•i-'i" ' '•' I 'I ' ' • • ' r 10 tS 20

Rgure 1. LC/ESI-MS mass chromatograms illustrating the composition of the cnjde reaction products of imidazoline synthesis (7h; boiling xylene);*" reactants oleic add and diethylenetriaine (DETA). i.e. R = Ct /Hss) . Mass chromatograms are: (a). Total ion current illustrating presence of all products l l - V I . ( bHe) . Molecular ion mass chromalograms for III, V + VI. II and IV. respectively. The presence of co-eluting diamides can be demonstrated by MS^ and MS^ as shown in Fig. 2. R = C,7H33.

the composition of the synthetic mixtures controls their self-assembly as monolayers on metal surfaces and hence their efficacy.*^

Much of the confusion seems to have arisen from the existence of different mechanisms in the solid-phase and solvent-based reactions.^** However, attempts to elucidate the mechanisms have also been hampered by the lack of sensitive, specific methods for identification of the reactants, intermediates and products i n the complex mixtures resulting f rom such reactions. Thus, even recent studies'" have required isolation and recrystallisation of the chemicals at each stage, followed by spectroscopic examination by nuclear magnetic resonance spectroscopy and other techniques. Powerful though these methods are, they are not sensitive to (perhaps important) minor products cmd intermediates, most of which are in any case removed by recrystallisation procedures. This may have led to some of the misleading conclusions concerning the mechanisms. It is not the purpose of this report to detail our investigations of the mechanisms, which w i l l reported elsewhere, but an example of an LC/ESl-MS mass chromatogram of a reaction mixture w i l l suffice to illustrate the util i ty of the present method. Thus, Fig. 1 shows the presence of monoamide (IV], so-called 13- (V] and 1,2-diamides [Vl |* and 2-alkyl-l-ethylamine-2-imidazolines [I I ] in addition to the 2-alkyl-l-[ethylalkylamide]-2-imidazolines (e.g. I l l ) in the crude synthetic products of the Dean and Stark reaction between oleic acid and DETA after 7 h. The identities of the major

The irivial names 1.2- and I.}- dlaniidcs arc in common use. The numbers refer to amide formation ai the lin.i and second nr tirM and ihinl nitrogen atoms, respectively, as shown in structures V and VI.

compounds were established either by co-chromatography wi th the isolated, recrystallised products, which were also characterised by infrared spectroscopy, or by interpretation of the multistage collision induced mass spectra, as we have reported previously.^

As an illustra'tion. Fig. 2(a) shows the M S ' mass spectrum of the reaction products of palmitic acid and DETA. Figure 2(b) shows the MS^ CIO niass spectrum of nt/z 580.6 wh ich is the mass expected for the 13- and 1,2-diamides [ V , V I ] . Al though both amides are isobaric, only the 1,2'diamide can lose ammonia by MS^ C I D to give the m/z 563.5 product ion observed in Fig. 2(b). MS^ CID of the m/z 563.5 involves an approximately symmetrical cleavage to m/z 282.3 (Fig. 2(c)), which on MS* C I D produces a m/z 95.2 ion (Fig. 2(d)). The m/z 562.5 MS^ C I D product ion also observed in Fig. 2(b) (inset) can be accounted for by loss of water and cyclisation to fo rm the qui te stable protonated 2 - a l k y M -(ethylalkyIamide]-2-imida2oline ion. Indeed, this is conf i rmed by MS"* and MS* C I D spectra (spectra not shown) product ions corresponding to our previously proposed ion trap CFD fragmentation pathway for 2-alkyl-l-(ethyl-alkylamide]-2-imida2oline.^ A i i ion at m/z 562.5 is also observed as the base peak in the MS^ C I D spectrum (Fig. 2(c)), which might be construed as evidence of loss of a hydrogen radical f r o m tii/z 563.5 (and therefore loss of a hydroxyl radical rather than ammonia f r o m the diamide parent). However, loss of hydrogen radical fo l lowing loss of hydroxyl was ruled out on the basis of further detailed MS experiments wh ich are not discussed here. We suspect the m/z 562 ion is in fact not a CID product ion at all since it was present at 0% activation ampli tude (AA) and the relative abundance remained constant at 31, 33 and (the

Copyright f 2002 John Wi\cy & Sons, Ltd. Kiifuil Coiiwiun. Mfjsa Sficclrvw. 2002; 16: 705-712

708 P. McCormack, P. Jones and S. J. Rowland

tea 200

• 100 -,

200 —p. 400

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P24 4

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138.1

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m* 562.5

As per reference 6

Art 95.2

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J COR

-NH,

COR

ffrt 563.5

COR

m/l 282.3

Rgure 2. Multistage mass spectra and proposed fragmentation pathway of compounds assigned as 1,2- and 1,3-diamides [m/z 580.6; VI. V]. The diamides were re-ciystallised from the solid-phase themial reaction products of palmitic acid with DETA (i.e. R = CisHa,). (a). Full scan m/z 50-700 mass spectrum of mixture of co-eluting 1,2- and 1.3-dlamides (VI.V). (b). MS^ spectnjm of daughter ions of m/z 580.6. Insert shows the formation of both m/z 563.5 attributed to loss of ammonia from the 1.2-diamide (VI) and m/z 562.5 attributed to loss of water from the 1.3-diamide (V). This demonstrates the presence of both V and VI in the reaction products, (c). MS^ spectrum of product ions of m/z 563.5 (1.2-diamide). (d). MS^ spectnjm of product ions of m/z 282.3 (1.2-diamide).

opt imum) 35% A A . Rather we suggest that the rn/z 562.5 ion was coincidentally isolated w i t h the m/z 563.5 ion. Unfortunately, attempts to prove this by reducing the isolation w i d t h f rom the normal tn/z 1 to nj/z 0.9 resulted in lower relative abundances for all ions and even lower isolation w i d t h values resulted In trapping of too few ions and signal instability. However, in a similar experiment w i t h a higher puri ty oleic acid derived d iamide {tii/z 632.6), the corresponding M-18 ion {nt/z 614.6 cf. 562.5) was not

Copyright c 2002 John Wiley Si Sons, Ltd.

present in the MS"* spectrum which supports our suggestion that 562.5 was not a C I D product ion.

In summary, f rom all the MS" spectra, two distinct ion trap CID fragmentation pathways can be identif ied (Fig. 2). It is proposed that one pathway is derived f r o m the 1,2-diamide by MS^ CID loss of ammonia. The second pathway is MS^ C I D loss of water w i t h cyclization f r o m the 1,3-diamide. Clearly, the LC/ESI-MS" method is very useful , particularly for examination of complex mixtures, and

Knftiit Coninitin. Masfi SfMrctmin. 2002; 16: 705-712

RCIVI .OOE-'OB

3.S0E+08

3 0 0 E ^

i 2.50E+O8

i 2.00E+OB

1.00E*O8

500E+O7

6

pg mL '

10 12

Rgure 3. Mass spectral ion cunen! response (m/z 614.7) of duplicate solutions of 2:1-Ol [III] in methanol (0.01 to 10.0 MgmL-').

allows the reaction progress to be monitored almost in real time.

Calibration of LC/ESI-MS response of 2-aIkyl-l-[ethylalkyIamide]-2-imidazolines The use of the LC/ESI-N4S method to measure the concentrations of imidazolines i n mixtures accurately, requires calibration of the MS response. This was achieved for 2-pentadecyl-l-IN-ethylhexadecylamidel-2-imida2oline (2:1-PI, I) and 2-heptadecenyI-l-[N-€thyloctadecenylamide]-2-imidazoline {2 : l -OI , I f l ) by measuring the molecular-ion (HV'Z 562.6 and 614.7, respectively) current response of a series of standard solutions (0.010 to 10.0 jig m L " ' ) of each in methanol (e.g. Fig. 3). The response was curvilinear and was subject to considerable day-to-day variation, thus illustrating the necessity for the synthetic compounds.

Recovery experiments Imidazolines are very prone to strong sorption to surfaces. Indeed, it this property which has led to their extensive deployment as corrosion inhibitors. The compounds coat the surfaces of metal oxides, reducing further access to water and other corrosive substances, the imidazoline group serving as a sufficiently strong Lewis base to displace water f rom the Lewis acid sites of the oxide surface."*^' This sorption behaviour may also influence the quantitative recovery of imidazolines during analytical chemical procedures. The compounds may sorb to particles in the oi l matrix (for example) and also to glassware, metal syringe needles, solid chromatography sorbents and other apparatus used in isolation methods. Ultrasonic dichloromethane extraction of freeze-dried sediments spiked w i t h (unstipulated concentrations oO 2:1-Pi and 2:1-01 imidazolines^ resulted in recoveries of >90% but we feel this may be concentration and matrix dependent, especially if active Lewis acid sites are present on mineral surfaces. To tr\' to assess losses dur ing our procedures we also undertook a series of recover)' experiments.

Copyright I 2002 John Wile>' & Sons. Ltd.

LC/ESl-MS to detect imidazolines in crude oils 709

Isolation and LCyESI-MS determination of 2:1-PI and 2:l-OI from hexane A 1:1 mixture containing I p g m L " ' each of pure synthetic 2:1-P1 and 2: l -OI was added to hexane and the imidazolines isolated f rom the SPE column in IPA/ammonia after sequential elution as detailed above in Materials and Methods. The experiment was conducted i n duplicate. L C / ESI-MS determination revealed a mean recovery o f 42 and 24% PI and O I , respectively, relative to the response obtained for the 1:1 mixture without SPE treatment. Obviously losses of the imidazolines to the apparatus are considerable and this method requires further optimisation to reduce the losses.

Isolation and LC/ESI-MS determination of 2:1-PI and 2;l-OI from crude oil A 1:1 mixture containing 1 j i g m L " ' ^ each of pure synthetic 2;1-PI and 2: l -Ol was also added to untreated (water-wet). Middle Eastern crude o i l . The imidazolines were isolated f r o m the spiked crude via SPE wi th IPA/animonia . The experiment was conducted in duplicate. LC/ESI-MS determination revealed only 37 and 25% (mean 31%) recovery of 2:1-PI and 4 and 2% (mean 3%) recovery of the added d i -unsaturated 2: l-OI at this spiking concentration relative to the responses obtained for the 1:1 nuxture wi thout SPE treatment. From the further reduction in recovery of the imidazolines f r o m wet crude compared w i t h their recovery f rom hexane (above; viz reduced f rom means of 42% to 31% PI and 24% to 3% Ol ) it appears that small amounts (ca. 1 pg) of imidazolines not only sorb strongly to some of the operational surfaces (most likely the metal syringe needles used for sample transfer), but probably also react w i t h the oil and /or are hydrolysed by the water in the o i l , which is known to be a rapid process.'^^^ The differences in PI and OI recovery probably reflect the different physical properties of the compounds (aqueous solubility, hydrolysis rates, sorp-t ivi ty) . A l k y I chain length is known to ir\fluence anti-corrosion behaviour (longer chains increasing inhibit ion) '^ suggesting that the sorptivities of the imidazolines do differ .

Nonetheless, despite these obvious disadvantages, the spiking method fol lowed by SPE and LC/ESI-MS appears to be both more specific and more serîtive than those published previously fo r determination of imidazolines i n crude oi l (e.g. Ref. 8) and w i t h further optimisation should be an important advance.

LC/ESI-MS characterisation of a commercial imidazoline-based corrosion inhibitor The ut i l i ty of ESI-MS^ fo r the characterisation o f imidazoline corrosion inhibitors has been demor\strated previously^*' and we have recently shown how multistage ESI-MS (MS*) is an even more powerfu l method for confirmation of imidazoline structures.^ Gough and Langley* also demonstrated L C / ESI-MS characterisation of 100 ppm concentratior\s of spiked imidazolines in production f luids (e.g. brines) f rom West Africa and the Nor th Sea. The detection and measurement of a 2: l -OI imidazoline | I I I | was clearly shown in the former, whilst, in the latter, the 1,3-diamide |V] and a monoamide (IV| were present, possibly due to hydrolysis i n the brine of

Raiiiii Coiunnni. Mnss Spectrotn. 2002: 16: 705-712

710 P. McCormack, P. Jones and S. J. Rowland

'l""l—T—I 0 5 10 15 20

Time (min)

RCIVI Base Peak

m/z- 100-1000 NL: 3.44E6

15.88 14.94

16.22

19.06

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100

50

I X

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15.27

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GI3J.613.3

NL: 3.44£6

fltO.2411.2

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Rgure 4. LC/ESI-MS mass chromatograms illustrating the composition of the imidazolines used in manufacture of a commercial con-osion inhibitor, (a). Base peak m/z 100-1000 ion current chromatogram. (b). 2;1-OI (m/z614) (c). 2-Heptadecenyl-1-(A/-ethylocladecadienytamide)-2-lmidazoIine. 2-heptadecadienyl-1-[AAethytoctadeceny1amide]-2-imidazoline (m/z 612) (d). 2-Heptadecadienyl-1 -[AAethyloctadecadienylamide]-2-(midazoline, 2-heptadecatrienyt-1-[A/-ethyloctadecenylamide]-2-lmidazoline and/or 2-heptadecenyl-1-(A/-ethyloctadecatrieny)amide)-2-(midazoline(m^z610) (e). 2-Heptadecadieny1-1-[Mettiyloctadecatrienylamide]-2-imidazoline and 2-heptadecatrienyl-1-[A/-ethyfoctadecadienylamide]-2-imida2oline (0-('). 2-Alkyl-1-ethylamine-2-imida20lines (e.g. II; rn/z350).

Ol [III] and 2-alkyl-l-ethylamine-2-imidazoIines (II] present in the synthetic ir\hibitor.

Prior to determination of an imidazoline-based corrosion inhibitor in a crude o i l (below) we also characterised the imidazolines of a commercial corrosion inhibitor by L C / ESI-MS (Fig. 4(a); 50MgmL~* in MeOH). The presence of not only 2; l -OI {ni/z 614; Fig. 4(b)), but also 2-heptadecenyl-l-(N-ethyloctadecadienylamidel-2-imidazoline{tii/z6\2: Fig. 4(c)), 2-heptadecadienyl-l-[N-ethyIoctadecenyIamidel-2-imidazo-line {m/z 612; Fig. 4(c)). 2-hepladecadienyl-l-|N-ethylocta-decadienylamideJ-2-imidazoline, 2-heptadecatrienyl-l-|N-ethyIoctadecenylamidel-2-imidazoline and/or 2-hoptadoce-

Copyright c 2002 John Wtk-y & Stins, Lid.

nyl-l-(N-elhyIoctadecatrienylanudeI-2-imidazoline(ni/z 610; Fig. 4(d)) was revealed by mass chromatography (Fig. 4). Indeed, the latter compounds w i t h tetraunsaturation in the alkyi chains were the major components (e.g. Fig. 4(a); retention time 15.27). Similarly, the presence of the 2-alkyl- l-ethylamine-2-imidazolines (e.g. I I ; m/z 350] could be demonstrated (Figs 4(0-(i)).

LC/ESI-MS determination of Ol-based corrosion inhibitor in crude oil A crude oil known to have been produced during use of an unsaturated acid-based corrosion inhibitor was examined by

R(i;i:(/ OHniimii. Mtti$ Spectrom. 2002; 16: 705-712

R C M LC/ESl-MS to detect imidazolines in crude oils 711

100

50 - \

S

100 -1

Time (mm)

Rgure 5. LC/ESl-MS mass chromatograms illustrating the presence in a Middle Eastern cmde oil ol 2:1-Ol (111; m/z 614.71. The concentration ot Ol could be estimated by comparison of the relative mass ion current responses of 2:1-OI im/z6U.7) and 2;1-P( (I; m/z 562.6] added to me oil at 1 f ig m L " ' The selectivity of the SPE isolation method combined with the resolving power of LC and the mass selectivity and sensitivity of ESI-MS makes this potentially a powerful method for the determination ol 'imidazolines' in crude oil.

the SPE and LC/ESI-MS method. A n aliquot of syntheHc 2:1-Pl (5 Mg m L " ' °'') was added as an interrul reference (Fig. 5). Obviously, given the 10:1 differential recovery of 2;1-PI over 2:l-OI (above), PI is far f r o m an ideal internal reference, but it probably represents the most appropriate surrogate available at present. Possibly synthesis of polydeuterated Ol compounds chosen to have non-isobaric molecular masses w i t h the analytes w o u l d produce better internal standards for future quantitative studies. Comparison of the integrated peak areas f rom mass chromatography for 2:l-OI {m/z 614.7; 313 relative response units) and 2:1-PI {m/z 562.6; 20 relative response uruts) al lowed an estimation of the concentration of 2: l-OI in the oi l (<0.1 MgrnL"* *"'). If the recovery of O l is only 10% of that of PI (as was found above at 1 ng m L " \ ° " ) then this value should be raised to < l M g m L " ^ of the individual 2-heptadecenyl-l-(N-ethyloctadecenylamide]-2-imidazoline (2: l -OI; I I I ) . Although this method is therefore only approximate and certainly requires further optimisation and replication, previous detenninations of individual imidazolines in crude o i l have not proved possible at all and delermirwtions of even >25ppm concentrations of total imidazolines are not routine,* The method is two orders of magnitude more sensitive than most and w i l l be important for operational and environmental uses. Indeed, given the complexity of the crude oi l substrate used herein compared to produced waters and sediments,^'**' the method may prove particularly useful for studies of tof>side discharges and environmental samples.

CONCLUSIONS

A semi-quantitative but sensitive and specific method.

Copyright -o 2002 John Wiley & Sons, Ltd.

involving SPE fol lowed by L C / ESI-MS", has been developed for the determiruition o f individual imidazolines at low (<10) parts per mi l l ion concentratior\s in crude oils. Whilst the method requires further optimisation due to the high experimental losses of imidazolines during work-up, it nonetheless represents a considerable improvement on previous techniques and should prove valuable for operational and environmental studies of corrosion inhibitor and surfactant behaviour.

Acknowledgements We thank AstraZeneca Brixham Envirorunental Laboratory and the University of Plymouth for a studentship, the NERC for firtancial suppHDrt for ESI-MS and Dr M . J. Hetheridge of AstraZeneca Brixham Environmental Laboratory for advice on LC/ESI-MS. We thank an anonymous industrial sponsor for provision of chemicals and an anonymous referee for he lpfu l suggestions which improved the original manuscript.

R E F E R E N C E S 1. Cole RB. Electrospray Ionization Mass Spectrometry-.Fundamen

tals, Instrumentation, and Applications. John Wiley: New York, 1997.

2. Puig D, Barcelo D, Silogoner I , Crasserbauer M. /. Mass Spectrom. 1996; 31: 1297.

3. Cough MA, Langley GJ. Rapid Commun. Mass Spectrotii. 1999;

4. Crescenzi C, Di Corcia A, Marcomini A, Pojana G, Samperi R. /. Oironiatogr. 2001; 923: 97.

5. Kidwell H, Jones JJ, Games DE. Rapid Cowmun. Mass Spectrom. 2001; 15: 1181.

6. McCormack P, Jones P, Helheridge MJ, Rowland SJ. Wn/cr Res. 2001; 35: 3567

Riifiitl Coiiniiun. Ma$$ Speclrtmt. 2002; 16: 705-712

712 P. McCormack, P. Jones and S. J. Rowland RCIVI 7. Grigson SJ, Wilkinson A, Johnson P, Moffat CF, Mcintosh

AD. Rapid Commun. Mass Spcctrom. 2000; 14: 2210. 8. Buck E, Sudbury JB. US Patent 5,152,177 Oct 6 1992. 9. Bislline RC Jr, Hampson JVV, Unfield VVM. MOCS 1983; 60:

823. 10. Wu Y, Herrington PR. JAOCS 1997; 74: 61. 11. Hofmann AW. Ber. Dlsdi. Ounn. Ces. 1888; 21: 2332. 12. Hampson JW. Bistline RG, Unfield WM. /AOCS 1983; 60:

1676. 13. Linfield WM. fAOCS 1984; 61: 437.

14. Martin JA, Valone FW. Nalional Association Corrosion En-ginefrs 1985; 41: 281. Ramachandran S, Tsai B-L, Bbnco M , Chen H, Tang Y, Goddard WA II . /. Phys. Oiem. A 1997; 101: 83. Ramachandran S, Tsai B-U BlaiKX> M , Chen H , Tang Y, Goddard WA II . Ungmuir 1996; 12: 6419.

17. Malik H. Br. Corrosion /. 1997; 32:150. 18. Swift AJ. Mikrodtiin. Acta 1995; 120:149. 19. McMahon AJ. Colloids Surfaces 1991; 59:187.

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Copyright r 2002 }ohn VVilcv £z Sons, Ltd. K(i;iii/ Coniitiiiii. MfJS. Spcclrvin. 2002; 16: 705-712

PI I : 80043-1354(01)00070-7

Wat. Res. Vol. 35. No. 15. pp. 3567-3578. 2001 ® 2001 Ehevier Science Ud. AD rights reserved

Prinicd in Great Britain 0043'1354/OI/S-sec front matter

PERGAMON www.clscvier.conVlocaie/waircs

ANALYSIS O F O I L F I E L D P R O D U C E D W A T E R S AND PRODUCTION C H E M I C A L S BY E L E C T R O S P R A Y

lONISATION M U L T I - S T A G E MASS S P E C T R O M E T R Y (ESI-MS")

p. M C C O R M A C K ' , P. J O N E S ' , M. J . H E T H E R I D G E - ^ and S. J . R O W L A N D ' * ' Plymouth Environmcnlal Research Centre, Dcpartmcni of Environmental Sciences. University of

Plymouth. Drake circus, Plymouth Devon, PL4 8AA, UK and ^Brixham Environmental LaborBtory. AsiraZeneca. Freshw-aier Quarry. Brixham, TQ5 8BA. UK

(First received 20 July 2000: accepted in revised form 22 January 2001}

Abstract—Large quantities of diverse polar organic chemicals are routinely discharged from oil production platforms in so-called produced waters. The environmental fate of many of these is unknown since few methods exist for their characterisation. Preliminary investigations into the use of multistage electrospray ionisation ion trap mass spectrometry (ES(-MS^ show its potential for the identificauon and quaniiiication of compounds in specialty oilfield chemicals (corrosion inhibitors, scale inhibitors, biodd^ and demulsificrs) and produced waters. Multiple stage mass spectrometry (MS") with both positive and negative ion detection allows high specificity detection and characterisation of a wide range of polar and charged molecules. For example. linear alkylbenzcnesulfonaies (LAS), alkyldimcthylbenzylammonium compounds, 2-alkyl-I-elhyhimine-2-imida2olincs. 2-alkyl-H/^-eihylalkylamide)-2-imidazolincs and a di-[alkyldimeihylammonium-ethyl]ether were all identified and characterised in commercial formulations and/or North Sea otlfteld produced waters. 77ie technique should allow the marine environmental effects and fates of some of these polar compounds to be studied. © 2001 Elsevier Science Ltd. All rights reserved

Key words—produced waters, oilfield chemicals, electrospray-mass spectrometry, corrosion inhibitor, multi-stage mass spectrometry

INTRODUCTION

When crude oiJ is produced f rom offshore oilfields it is associated with varying proportions o f water called formation waters (Warren and Smalley, 1994). In the early stages of oil production, the water content is usually low whereas later the proportions can rise to as high as 80% (Tibbetts et al., 1992). Once the water has been separated from the oil it is known as produced water (PW) and this is discharged into the sea (Ray and Engelhart. 1992; Reed and Johnsen, 1996). PW discharges on the U K continental shelf rose from about 5S million tonnes in 1984 to about 145 million tonnes in 1994 and since 1994 have increased still further (Stagg ei al., 1996).

The oil recovery,, production and separation processes involve addition o f a diverse mixture o f oilfield chemicals (OCs) to the oil-water mixtures. For example, these chemical mixtures are formulated to act as scale inhibitors to prevent mineral scale deposition blocking pipework, corrosion inhibitors to prevent pipe work from attack by the salt water

'Author to whom all correspondence should be addressed. Tel.; +44-1752-233013: fax: +44-1752-233035; e-mail: s.rowland(o plymouth.ac.uk

and dissolved gases, biocides to prevent bacterial degradation o f the oil and other products, and emulsion breakers to facilitate oil-water separation (e.g. Reed and Johnsen, 1996). Some or all o f these OC:s may be discharged to the marine environment along with the PW (van Zwol , 1996; Slager et at., 1992; Stephenson et a/., 1994; Flynn et al., 1996). In the Nor th Sea an estimated 5934 tonnes o f OCs were discharged in 1989 along with an estimated 84097 tonnes o f drilling chemicals (Hudgins, 1994).

Although the syntheses of the individual components o f the formulated oilfield chemicals rely substantially on well-known chemical reactions, the products f rom individual companies may differ due to blending in order to achieve different activities and functions. Many of the organic chemicals in the OCs are polar, hydrophilic compounds, which are not amenable to routine analysis (Martin and Valone, 1985; Cough et ai, 1997; Cough and Langley, 1999). Establishment o f such methods is therefore important to the OC manufaciurers, to the oilfield operators and to scientists concerned with the fate and effects, i f any. o f PW and OCs in ihc marine environment (e.g. Gamble et aL 1987; Washburn et a!., 1999).

Previously, fast atom bombardment—mass spectrometry (FAB-MS) has been used to good effect to

3567

3568 P. McCormack ei al.

partially characterise OCs in PW (Tibbelis et al., 1992) and other spectroscopic methods have been used in attempts lo characterise oilfield chemicals such as imidazoline corrosion inhibitors (Mar t in and Valone, 1985). Recently, ciccirospray ionisation mass spectrometry (ESI-MS) has also proved to be a powerful method for the identification o f some constituents o f OCs (Gough and Langley, 1999). Here we report that improved characterisation o f numerous polar organic chemicals in OCs and in PW samples f rom North Sea oilfields is possible by use o f both positive and negative ion multistage MS with ES ionisation ( (±)ESI-MS' ' ) . The method promises to be useful for monitoring the fate o f OCs in oilfield operations and in the marine environment.

EXPCR (MENTAL

Chemicals Ultra pure water was obtained from an Elgasiai (EJga.

High Wycombe, UK) filtration system. All solvenis used were of H P L C grade. Methanol and acetonitrile (Hypcr-solv) were obtained from BDH (Poole. U K ) , and dichloro-mcihanc (DCM) from Rathbura (Walkcrbum. UK.). Dodecylbenzenesulfonic add (DBSA) sodium salt was purchased from Aldrich (Dorset, UK.) and benzyldimcthyl-tciradecylammonium chloride from Ruka (Buchs, SW).

PW samples were supplied by various North Sea oilfield operBiors and specially OCs by various manufacturers.

Mass spectrometry

Mass spectrometry analysis was carried out using a ThcrmoQucsi Finnigan Mat L C Q (Sa'n Jose, C A . USA. ) bench top mass spectrometer fitted wiih an electrospray interface. Navigator I.I software was used for the PW and DBSA samples with a full scan range of m/r SO-1850. All other samples were run with Xcatibur 1.0 software in the normal full scan range (m/2 SO-2000) (following an instrument hardware upgrade). Instrument tuning and mass calibration was carried out and checked using the automatic calibration procedure (tuning and calibration solution-caffeine, M R F A , and Ultramark 1621 in methanol: water: acetic acid (50:50:1, v/v/v)). Infusions of PW extracts and O C solutions were carried out using a built in syringe pump with a Hamilton I725N (250^1) syringe (Reno C A . USA. ) . Analyics were infused at Sjilmin"'. Source voltage, ( ± ) 4.5 kV; capillary Voltage ( ± ) 0-50 V (auto tunc function on ion of interest); capillary temperature, 200*C; nitrogen sheath gas flow rate, 40 (arbitrary units). ( ± ) MS" analysis of selected ions was performed in the ion trap by collision-induced dissociation (CID) with helium. MS" ion isolation widths, relative activation amplitudes and activation Q, were optimised to obtain high response and stability of the base peak fragment ion. High-resolution zoomscans (ZS) were recorded for all ions of interest. All spectral data was recorded and averaged over a I-min acquisition time.

Produced waters

PW samples were extracted with D C M (-50 ml). One extract (PW60) was blown to dryness with nitrogen and the residue re-dissolved in 500^1 methanol and 2S0fil Ultra pure water (PW60MW). A D C M extract from a difTercni PW (PW90) was reduced to - I ml using a Kudcrna Danish controlled evaporation and the remaining extract was divided into two portions (-^^.Sml) in prc-wcighed vials and blown down lo dryness with nitrogen. The dry residues were re-dlssoKcd in methanol ( Iml; PW90M)

and acetonitrile (I ml; PW90A). A further 900 jd A C N was added to lOOpI of PW90 A for analysis.

Stock solutions of standard compounds Dodecyl benzenesulfonic acid (DBSA) sodium salt

(50 mg) was prepared by dissolution in Ultra pure water and made up to 50 ml. Bcnzyldimcthylietradecylammonium ( B D M T D A ) chloride (50 mg) was made up to 50 ml with methanol. Dilutions of the stock u-ere made using the required solvents.

Oilfield chemicals Stock solutions of commercial products were prepared as

follows: Cbn-osion inhibitor C1-D2 (50^l) was diluted to 50 ml with M c O H : H i O (1:1. v/v); Corrosion inhibitor C l -A3 (25 mg) was made up to 50 ml with MeOH; Corrosion inhibitor C l - B l (II6mg) was made up to lOOml with MeOH; Corrosion inhibitor C I - C 3 (100;il) was made up to 10 ml with MeOH; Dcmulsifier DM-C2 (25 mg) was made up to 50ml with MeOH. Dilutions of the stock solutions wxre made using the required solvents.

RESULTS AND DISCUSSION

Produced waters

Discharged PW is a complex mixture of liquid and particulates and comprises inorganic and organic compounds of natural origin, applied production chemicals (OC^), and residues o f other platform effluents and deck washes. For an initial evaluation of ESI-MS" as an analytical technique for PW analysis, D C M extracts were used to obtain polar organic fractions. After removal of D C M , the extracts were re-dissolved in various solvents (e.g. methanol, acetonitrile or methanol/water) as it is well known that electrospray ionisation o f compounds varies for different solvents. Negative and positive ion ful l scan spectra [m/z 50-1850], ZS and C I D MS" spectra of significant ions were acquired in order to provide data that could be used to identify the unknown extracted compounds.

In general, negative ion spectra of PW extracts were relatively simple with low baseline noise. Ions at mfz 297, 311, 325 and 339 were the only significant ions in extracts dissolved in methanol/water and methanol. The spectrum of an extract dissolved in acetonitrile (Fig. ( l A ) ) also contained these ions but in addition a series of ions differing by 14 Da in three clusters were apparent at mfz 423, 529 and 635. Compounds that, correspond to ions in the clusters are still to be identified but C I D MS" analysis o f the ions at m/z 297, 311. 325 and 339 (base peak) indicated a common structure differing only by 14 Da. Thus, CID MS^ of precursor ions m/z 297, 311, 325 and 339 produced neutral fragment losses to give a common product ion m/r 183 in each case (e.g. Fig. 2(A)). CID MS^ of the m/r 183 product ion in each case produced a fragment ion m/z 119, representing loss of a neutral 64 Da fragment (Fig. 2(B)). Further fragmentation (MS^) of the m/z 119 ions produced no detectable ions.

ESI-MS" analysis of oilfield produced waters

339.7

340.9

3569

530.0

311.7 543.8

557.9

635.8 297.9

717.6

628.6

628.6

100 -3

621.7 565.7

626.5

577.7

622.8

I 624.71 753.5 B30.8

.74.4 230.5 619.6 o 40 d

913.1 1180.7

1390.3 1687.1

Fifi. I. Negative (A) and positive (B) ion ESI-MS mass spectra of produced water extracts: (A) A C N solvent and (B) MeOH solvent.

The precursor ions m/z 297, 311 325, 339 and the CID MS^ product ion m/z 183 arc consistent with those expected of linear alkylbenzencsulfonates (LAS) (Fig. 2(C), (i)) (Lyon et a!., 1998; Schoder. 1996; GonzalezMazo and GomezParra, 1996; Gon-zalezMazo et ai., 1997; Reemtsma. 1996; Rieu et a/., 1999). The MS^ fragment iori m/z 119 produced from the C I D o f (he m/z 183 product ion via a neutral loss of 64 Da is consistent with loss of sulfur dioxide (SO2) f rom an elhylenebenzenesulfonale ion (Fig. 2(C), (ii)) to yield an ethylenephenoxy ion (Fig. 2(C), (iii)). The fragmentation pathway shown in Fig. 2(C) could be deduced for the MS^ CID of LAS. To our knowledge the M S ' mjz 119 fragment ion produced by loss of SO2 from the C I D of the MS^ mjz 183 product ion has not been reported previously. In order to confirm that the peaks are due to alkylbenzenesulfonates a commercial sample of

dodecylbenzenesulfonic acid sodium salt was also examined. The negative ion fu l l scan spectrum showed the same four main ions {m/z 297, 311, 325 and 339), whilst MS" produced identical fragment ion losses from each precursor ion to those shown in the PW components. The negative ion mass spectrum of an oilfield demulsifier DM-C2 (Fig. 3(A)) also contained ions at m/z values consistent with the presence of alkylbenzenesulfonates. MS" analysis showed fragmentations identical to the dodecylben-zencsulfonic acid sodium sail. Thus, ESI-MS" allows unambiguous identification o f linear alkylbenzenesul-fonaies in both PW and OCs.

The positive ion spectra of the PW extracts were more complex than (he negative ion spectra and the spectrum of (he ex(ract dissolved in methanol was very 'noisy'. This is expected, as (he ionisa-(ion efficiency of many compounds is greater in

3570 P. McComiack ei al.

100

00

so

70

60

50 q

40

30

20

10

0

183.1

119.3 170.3

164.1

7p .1 239.1 275.3

L

340.2

mlz 1 3 ,

100 -00

80 \

f

70 \ f 60 3

SO

MI

II

I

£ 40 1 S z n tL

30

20 i 10 i 0

110.2

80.0

55

Precursor ion

B

183.1

•3* AtSO m/z

MS2

l-OSSOf akylctiain

R = C«H„. C ^ ^ C«,H„ and C„H„

mte 297.311.325and339

Loss of (ii) , I

Product ion

nVz 183

Fragment ion

m / i 1 1 9

Fig. 2. Negative ion ESI-MS" spectra of pnxursor ion m/z 339.7 shown in Fig. 1(A) for produced water and CID MS" fragmentation pathway of alkylbenzencsulfonalcs; (A) MS^ spectrum of the precursor ion m/z 339.8; (B) MS* spectrum of the m/z 183 produce ion and ( Q CID MS" fragmcnUilion patliway of alkylbcnzencsulfonates. MS^ cleavage of the alkyi chain is al ihc same position for all homologues

producing idcniical product ions.

melhanol/water mixtures rather than pure methanol. The spectra of extracts dissolved in methanol (Fig. 1(B)) and acetonitrile were very similar with a base peak ion at m/z 628 with a distribution o f ions differing by 2 Da. This is consistent with the presence of two homologous series of compounds, one containing a further degree of unsaturaiion. The spectra are consistent with a diamidoamine synthe

sised from tall oil fatty acids (TOFA) and diethyle-neiriamine (DETA) (Gough and Langley, 1999). Such amides are commonly produced during the manufacture of imidazoline corrosion inhibitors. Also imidazoline compounds readily hydrolyse to their amide precursor compounds on exposure to air (Lomax, 1996) and might therefore be produced in PW from hydrolysis of an imidazoline-based pro-

ESI-MS" analysis of oilfield produced waters 3571

100

90 z

BO -.

g 70 T

leo^ | so I 40

1 3 0

20 -.

10 \

0

311.3

297.3

183.1

3 2 5 J

3 3 9 J

353.2 637.1 6B7.2 1001.5 1166.2 1445.6 1632.0

- T - ' - l ' " T ^ I 1 " ^ - ' . • I - " ' 500 1000

mtz 1500 2000

100

90

80

I ^

I " I 40 -3 I 30

20

10

0

664.7 703.7

620.7

576.7

532.7

488.7

4445 1 1 1 . 3

175.1 - | I 500

752.8

7967

840.8

884.6

928.8

972.9 1092.7 1344.0 1694.2 1842.7

1000 mtz

1500 2000

Fig. 3. Negative (A) and positive (B) ion ESI-MS mass spectra of DM-C2 oilfield demulsificr (7:3 v/v M c O H : H ; 0 ) .

duct. Ions at m/z 489.7, 533.7, 577.7. etc. differing by 44 Da (Fig. 1(B)) are tentatively attributed (o polyethoxylated compounds, typical o f those found in commercial de-emulsifiers (Lomax, 1996).

Oilfield chemicals (OCs)

A wide range of OCs are used in offshore oil and gas production. Most are complex mixtures derived from impure raw materials (Hudgins. 1992). Furthermore, many commercial products arc blends of (wo or more chemical (ypcs. For reasons of commercial confidentiality, the specific chemicals and quantities contained in oilfield products are not generally made public and only the legally required health and safely data arc normally specified on material safe(y dao sheets (MSDS). The information given regarding (he active chemicals is generally restricted to the class of compounds (e.g. amines, quaternary amines, imidazolines, polycarboxylates, phosphonaies) and the solvents (aqueous, methanol or aromatic solvents). Without

detailed knowledge o f the OC compositions or the availability of suitable analytical methods, it is difficult for the fate of OCs in operational processes or in environmental scenarios to be followed. ESI-MS" methods begin to allow such knowledge to be assembled, particularly i f the mass spectra can be interpreted to identify unknown constituents, as illustrated in the following experiments in which samples of commercial OCs were dissolved and diluted in appropriate solvents and analysed by direct infusion ESI-MS".

Corrosion inhibitor C/-D2: C/-D2 is a commercial oilfield corrosion inhibitor slated loconUin (MSDS) fatly amine quaiernary sal(s (10-30%) in water and methanol (10-30%). A + E S I f u l l scan mass spectrum (Fig. 4(A)) of CI-D2 dissolved in methanol: water ( 1 : 1 , v/v) solvent, showed three distinctive odd m/z ion series. Ions in the most intense scries centred on m/z 249 dilTered f rom each other by m/z 14, whilst (hose in (he series around m/z 533 and 1131 differed by m/z 28. These differences between ihe scries were

3572 P. McComiack ei at.

100

00

60

70

j e o

a 30

20

10

0

214J

165.2

203.4

200

277.4

320.3

533.3

561.4

560.5

617.5

600

645.6

673.5 6 635.7

1131.7

1075 7 , . 9 i27.ve

1729.6 1973.5

2000 400 600 1000 1200 1400 1800

1:

•

-. B

A

Ml* j Ml* j

Fig. 4. Positive ion ESI-MS mass spectra of CI-D2 oilfield corrosion inhibiior (1 :1 v/v MeOHiHiO): (A) Full scan m/z 50-2000; (B) ZoomScan m/z 249.4 and (C) ZoomScan m/z 533.4.

elucidated by the use of the so-called 'zoomscan* (ZS) facility on individual ions in each series. ZS allows resolution of isotope peaks for up to + 4 charge-stale ions. Thus, pairs o f ions in the series at m/z 221.4-305.4 (e.g. m/z 249.4 and 249.7) showed mass differences of 0.4 Da (Fig. 4(B)). The m/z 249.3/ 249.7 ion ratio was consistent with that expected for '^C/'^C isotopes. There is no evidence for the presence o f chlorine or bromine. The 0.4 Da mass differences suggest the m/z 221.4-305.4 ions are doubly charged ions (M^"' /2) . By contrast, ZS analysis o f the ion series m/z 477.5-645.5 shows mass differences of I.ODa between ion clusters (e.g. m/z 533.4/534.4; Fig. 4 ( Q ) consistent with singly charged ions ( M * / I ) . However, whilst the m/z 533/ 534 ratio is also consistent with that expected for '^C/'^C isotopes, the 3:1 ratio of m/z 533 and 535 is also indicative o f the presence o f a chlorine atom (viz: " C I / " C I ) . A n odd m/z value for the ions indicates that an even number of nitrogen atoms is preseni. As fatty amine quaternary salts are expected from the MSDS descripiion. identification of the compound as a di-quaternary salt is consistent with all the spectral data (viz: ion series at m/z 221-305 due to

M 2 + . m/z 533 ( M ' ^ ' + C r ] " " and m/z 1131 [2M2'^ + 3 C r ] * ) -

In an attempt to identify the chemical more completely, MS" analysis o f the ions observed in the fu l l scan spectrum was carried out. Highly reproducible product ion spectra were obtained for ions attributed to M^ând [M^*+Crj"*^ wiih up to five C I D fragmentation steps (MS^ Fig. 5). A fragmentation pathway and a molecular structure for the precursor ion at m/z 533.5, consistent with the MS" data (Fig. 5(A)-(D)) is shown in Fig. 6. The structure is consistent with known synthetic routes to Au-quatemary ammonium compounds, involving reaction of fi-dichloroethylether wi th alkyl dimeihylamine (Linfield, 1970). Thus, i f the fatty amine was derived from a coco or palm oil source (cf Gough and Langley. 1999) then all the possible ions resulting from combinations of Cs.io.iz.M.ie.is alkyl groups can be identified in the mass spectrum (Table 1).

Corrosion inhibiiors C/-C3 and C/-B1: CI-C3 and C I - B l are commercial oilfield corrosion inhibitors stated (MSDS) to comprise: eihoxylaied amines and

ESl-MS" analysis of oilfield produced u-aicrs 3573

113.0

Fig. 5. Positive ion ESI-MS" mass spectra of precursor ion m/z 533.4 in spectrum Fig. 5 for C I - D 2 oilfield corrosion inhibitor (A) MS^ on precursor ion m/r 533.4- (B) MS^ on product ion mfz 483.4; (C) MS* on

product ion m/r 270.2 and (D) MS^ on product ion m/z 226.2.

quaternary compounds (5-10%), butyl glycol (20-30%) and monoethylene glycol (20-30%) in water (CI-C3) and benzyl chloride quat amine (5-10%) and methanol (1-5%) (CI-Bl) . Positive ion ESI-MS spectra suggest that both formulations contain quaternary amines corresponding to alkylbenzyldi-methylammoniura (benzalkonium) compounds (Figs 7(A) and (B)). The spectra show that the alkyl chain source is different for each product, with Ci-C3 having a C|2 (base peak), C u . C|6 and Cis distribution whilst CI-BI has only two ions for Ci6 and C|8 (base peak). This has been shown previously by ESI-MS (Cough and Langley, 1999). The more powerful multi-stage MS" analysis of the benzalk-oniimi ions produced highly reproducible fragmentations with masses differing only by the alkyl chain lengths. Thus, C I D MS^ o f the benzalkonium precursor ion produced two fragment ions (Fig. 8(A)) with the base peak m/r corresponding to a neutral loss of 92.0 Da, consistent with fragmentation o f the benzyl moiety with a proton migration to effect loss o f a methylbenzene and yield an iminium ion (Fig. 8(C)). The fragment at m/z 91.0 is consistent with a benzyl cation (tropylium ion) commonly seen in electron ionisation-MS of aromatic compounds, and a neutral loss of alkyldimelhylamine (Fig. 8(C)). Both of the MS^ fragment ions result from cleavage of the same nitrogen-benzyl bond. C I D MS^ o f the MS^ iminium ion (Fig. 8(B)) results in loss of an alkene molecule via a 1.5 proton shift McLafferty rearrangement (De Hoffmann et ai. 1996) to yield a

mfz 58 iminium ion (Fig. 8(C)). MS" analysis of authentic benzyldimethyltetradecylammonium chloride ( B D M T D A C I ) produced identical fragmentation spectra to those for the benzalkonium ions in the corrosion inhibitors. The reproducibility o f the C I D MS" spectra allows unambiguous identification of the benzalkonium ions.

Corrosion inhibitor CI-C3 also contained ethoxy-lated amines (MSDS). Ions due to these arc also seen in the ( + )ESI-MS spectrum (Fig. 7(A)) as at least three series of ions differing by 44 Da {viz: corresponding to -C2H4O-) between m/r 500-1300. Although the MSDS for corrosion inhibitor CI -BI does not state that it contains ethoxylated compounds there are clearly several series of ions differing by 44 Da in the spectrum and some have similar m/z values to those seen in CI-C3 and in the demulsifier DM-C2 (Fig. 3(B)). The even m/z ions infer an odd number o f nitrogen atoms in the compounds and the presence of several series suggests that both CI -BI and DM-C2 contain ethoxylated amines. Scries differing by 44 Da are also observed in positive ion ESI-MS spectra o f the produced waters (e.g. Fig. 1(B)), suggesting these demulsifiers may be discharged into the environment. However in the PW the ethoxylated compounds differed by I Da (reliably measured by ZS) from those in DM-C2 and CI-C3.

Corrosion inhibitor CI-A3: Corrosion inhibitor CI -A3 is a commercial oilfield corrosion inhibitor with a staled composition (MSDS) comprising 10-15%

3574 P. McConnack ei al.

Precursor ion m/z 533.4 Fragment ion ni*329.3

H , , C „ - ^ ^ N - C - C - 0 ^ - C - N

'CI MS2

H„C, /^N-C-C-0-C-CjN-

Product ion m/z 270.2 e

H 2 i C , i ^ - N - C - C O - C = C H , ^

^ N ^ ^ C ^ , MW;213

Product ion mfz 226.2

MS3

N-C=C

O^g-CHj MW:44.0


H , c | -C=CH, . H,.C.-C=CH,

* a - C ^ «W:204

Fragment ion m/^320.2

N-c-c-o-c-c-a

MW:213

Product Ion 483.5 d

N-C-C-O-C-C N-

Fragment ion m/^ 102.1

H-N-C-C-0-C=CHj

H„C,,-C=CH, Mw:i6a


H H-N-C=C + H3,C„-S=CHj

CH3 H MW: 168

Fig. 6. Positive ion CID ESI-MS" fragmentation pathway of precursor ion m/z 533.4 in spectrum Fig. 4(A) and MS" spectra Fig. 5(A>-{D) for CI-D2 oilfield corrosion inhibitor.

Table I . Isoiopic Masses for{M'* +"a"J where Rl and R2 arc alky) moicdes derived from coco or palm oils

H3 C C

Rl - N * - C - c-o-c- C - N * -

C C Hi

RI/R2 c, C,o Cu C,6 c„

c. 421.4 449.4 477.5 505.5 533.5 561.5 449.4 477.5 505.5 533.5 561.5 589.6

c„ 477.5 505.5 533.5 561.5 589.6 617.6 Cu SOS.S 533.5 561.5 589.6 617.6 645.6

533.5 561.5 589.6 617.6 645.6 673.7 c„ 561.5 589.6 617.6 645.6 673.7 701.7

solvent naphtha (petroleum), 1-5% butoxycihanol and 20-40% long chain alky! imidazoline. A positive ion ESI full scan spectrum (Fig. 9} of a solution of CI-A3. contained two prominent sets of ions at mjz 350 and 612. These are near identical to those reported by Gough and Langley (1999) for T O F A / DETA-derived imidazolines. Gough and Langley attribute the spectra to proionated 2-alkyl-I-«ihyl-amine-2-imidazolines'. and 2-alkyl-l-[yV-ethylalkyl-amidel-2-imidazolines (Fig. 9). The peak distributions differ by 2 Da in each group, which is consistent with a natural distribution of unsaturated acids expected from reactants derived from a natural source such as a Tall Oil. MS^ analysis of the precursor ions m/r 3S0.7 and 614.7 (Fig. 10(A) and (C)). corresponding to imidazolines with alkyl moieties R r = C i 6 H 3 i and R2 = C|7Hj3, shows the formation of a protonaled 2-alkylimidazoIine moiety

ESI-MS" analysis of oilfield produced waters 3575

304.5

332.5 B 7 2 J

\04BJ6 1092.7

1136.8 1180.8

B09.e ^388.6

639.B 1523J 258.4 1917.1

2000

ICQ

S70 € 60 c I 50

I ^° & 30

20

10

. 0

388.6

360.7

296.6 234^ 897.5

1202.9 1291.7 1684.5 1959.8

500 p .

1000 mtz

' I " T " 1500 2000

Fig. 7. Positive ion ESI mass specira of oilfield corrosion inhibitors (A) CI-C3 and (B) CI-BI (1:1 v/v McOHiHiO).

(Fig. 10(E)) as the base peak ion for both ions via losses of etheneamine and N-ethene-alkylamide, respectively. MS^ fragmentation of the product ion m/z 307 (Fig. 10(B) and (D)) produced identical spectra consistent with the loss of the alkyl chain to give a protonated 2-ctheneiniidazoline (Fig. 10(E)). Further fragmentation produced no ions above the m/z 50 lower mass limit of the instrument. Spectra were obtained for other ions in the two groups producing product ions that varied by 2 Da, confirming the difTerences were due to the degree of unsaluration of the alkyl chains. A fragmentation pathway that is consistent with the structures of the imidazoline compounds is given in Fig. 10(E).

CONCLUSIONS

Examination of a range of oilfield chemicals (OCs) and of oilfield platform produced waters (PW) by elecirospray-ion trap-mass speciromeiry has demonstrated that the technique is very powerful for the identification of polar chemicals

used as demulsifiers, corrosion inhibitors and bio-cides, for example.

A range of imidazolines, alkylbenzene sulfonates, quaternary ammonium compounds (quats) and ethoxylates have all been identified, some for the first time in OCs and PW.

The particular advantages of the ion trap multistage MS method are: the possibility of both positive and negative ion detection (e.g. for quats and sulfonates, respectively); the ability through the so-called *ZoomScan' facility to determine the accurate mass difllerences between ion pairs, thus allowing difTerentialion of the multiple charge state of the ions; the coIIisionMnduced dissociation multistage mass spectrometry allowing fragmentation pathways to be studied in up to five steps, thereby allowing previously unknown compounds to be identified.

Coupled with liquid chromatography, the ESI-MS" method promises to be valuable for studies of the operational use and the environmental fate of a range of OC^ in oil production chemicals and produced waters.

3576 P. McCormack et at.

too 00

•0

8 " I '° I " i :

20

to 0 J * 2Sb Mb id> *A «!D Idb

an

i n •0

•0

i : I so

to. 0 .

H-B I I 1.1

B

Precursor ion

mft 304.4 R = CBH,g

N— //

MS2

- a -

Fragment ion m/z91.0

Fragment ion M W : 154.2 Product ion mft 212.3

^^W: 213.3

MW: 92.0

Fig. 8. Positive ion ESI-MS" mass spccira or ion m/z,304.4 in specirum Fig. 7 and CID MS" frarancnution pathway for CI-C3 oilfield corrosion inhibitor: (A) MS on precursor ion mfz 304.4; (B) M ? on product ion mfz 212.3; ( Q CID fragmentation pathway for alkylbcnzyidimcthylammonium ions.

348.6 612.6

350.6 H N y N

R l 610.7

2-AlkyH -ethyIamine-2-Imida20line

614.6

N R2

305.6 351.6

2-AIky»-1 -{N-ethy)a!kylamide)-2Hmidazoline

1286.5 1391.5 1602.6

630.5

636.6 960.1

Fig. 9. Positive ion ESI-MS mass spectrum of CI-A3 oilfield corrosion inhibitor (90:10:0.1 v/v/v MeOH:H;0:AcOH).

- 70

A a

I "

(3)

•0

•0

TO J

1 w

( ^ )

ESI-MS" analysis of oilfield produced waters

A

3577

C

B

4)

I to

u M 40i.» U2.;

t9J> jtOM 4 ^ m j 2 J I J

'idL 1^

D

I T

(1) H N * ^ i ) ^ ^ ^ ^

R1 J

mTz 614.7 Rl =C,BH„

R2 = c,^«

Loss of

Loss of O N R2

(3)

H N ^ N H

J/ R1

mft 307.2

Loss of AOcyl group

(4)

rrn

fn/z97.0

E

Fig. 10. Positive ion ESI-MS" mass spectra of ions mfz 350 and 614 shown in Fig. 9 and CID MS" fraemcntation pathway for CI-A3 oilfield corrosion inhibitor: (A) MS^ on precursor ion m/z 350.7; (B)

on product ion m/z 307.2 in A; (C) MS^ on product ion m/z 614.7; (D) MS' on product ton m/z 307.2 in C and (E) proposed CID fragmentation pathway.

Acknowledgements—'^t arc grateful to AstraZeneca Environmental Laboratory and the University of Plymouth for a research studentship (P. McCormack), and to the sponsors of the NERC/industry-funded MIME programme for access . to Produced Waters and oilfield chemicals. Dr P. Ncstcrenko (Moscow State University) is acknowledged for helpful discussions.

REFERENCES

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Flynn S. A.. Builcr E. J. and Vance i . (1996) Produced water composition toxicity and fate. In Produced Water 2. Environmental Issues and Mitigation Technologies, eds

M. Reed and S. Johnscn, pp. 69-80. Plenum Press, New York.

Gamble J. C . Davies J. M.. Hay S. J. and Dow F. K. (1987) Mesocosm experiments on the effects of produced water

• discharges from offshore oil platforms in the northern North Sea. Sarsia 72, 38S-386.

GonzalezMazo E. and GomezParra A. (1996) Monitoring anionic surfactants (LAS) and their intermediate degradation products in the marine environment. Trends Anal. Chem. 15. 375-384.

GonzalczMazo E.. Honing M., Barcelo D. and GomezParra A. (1997) Monitoring long-chain intermediate products from the degradation of linear alkylbenzcne sulfonates in the marine environment by solid-phase extraction followed by liquid chromatography ionspray mass spectrometry. Environ. Sci. Technol. 31. 504-510.

3578 P. McCormack et at.

Cough M . A.. Ungley G. J.. Hedges W. M. and Byrne N. E (1997) Analysis of oilfield chemicals by elecirospray-mass specirameir>-. Eighrtt Intemaiionat Symposium on Oil Field Cfjemicals. March 2-5. Ccilo. Norway.

Cough M . A. and Langley G. J. (1999) Analysis of oilfield chemicals by elecirosprBy-mass spectrometry. Rapid Commun. Mass Specir. 13. 227-236.

Hudgins C. M . (1992) Chemical treatments and usage in offshore oil and gas-production systems. J. Petrol. r « W . 44. 604-611.

Hudgins C. M . (1994) Chemical use in North Sea oil and gas E & P. y. Petrol. Technol. 46, 67-74.

Lomax E. C. (1996) Imidazoline derived amphoterics. In Ampftoieric Surfactants, cd. E. G. Lomax, 2nd edn.. p. )9S. Mara l Dekker. New York.

Unfield W. M. (1970) Organic chemistry of cationic surfactants. In Cationic Surfactants, cd. E. Jungermann p. 30. Marcel Ctekker. New York.

Lyon P. A.. Stcbbings W. L.. Crow F. W.. Tomer K. B.. Lippstrcu D. L. and Gross M. L. (1998) Analysis of anionic surfactants by mass spectrometry/mass spectrometry with fast atom bombardment. Anal. Chem. 56. 8-13.

Martin J. A. and Valone F. W. (1985) The existence of imidazoline corrosion inhibitors, ^'at. Assoc. Corr. Engs. 41.281.

Ray J. P. and Engclhart F. R (1992) Produced Water. Plenum Press. New York.

Reed M . and Johnsen S. (1996) Produced Water 2. Emjironmental Issues and Mitigation Technologies. Plenum Press, New York.

Reemtsma T. (1996) Methods of analysis of polar aromatic sulfonates from aquatic environments. J. Ctiromatogr. A 733. 473-489.

Rieu J., CoazalczMazo E.. ComezParra A. and Barcclo D. (1999) Determination of parts per trillion level of carboxytic degradation products of linear alkylbenzene-

sulfonates in coastal water by solid-phase extraction followed by liquid chromatography/ionspray/mass spectrometry using negati -c ion detection. Chromotograpbia SO. 275-281.

Schoder H. Fr. (1996) Selective determination of nonbiodegradable pobr. organic fwltuiants in waste u-ater related to functional groups using flow injection combined with tandem mass spectrometry. Water Sci. Technot. 34. 21-28.

Slager L. K.. \-an Hattum B., Tromp Mecstcrs M. . Scholten M . C. Th.. Kaag N. H. B. M.. Cofino W. P. and Fcenstra J. F. (1992) Erwironmental Aspects of Produced Water Discharges from Oil and Gas Production on the Dutch Continental Shelf pp. I-I03. Institute for Environmental Studies, Amsterdam. NOGEPA.

Stagg R.. Gorr D. J.. Whale G. F.. Kirby M . F., Blackburn M. . Bifield S.. Mcintosh A. D.. Vance I . . Flynn S. A. and Foster A. (1996) In Produced Water 2. Environmental Issues and Mitigation Technologies, cds M . Reed and S. Johnsen. pp. 81-100. Plenum Press, New York.

Stephenson M. T. el al. (1994) North Sea Produced Water: Fate and Effects in the Marine Environment. E & P Forum. Report No. 2.62/204.

Tibbetis P. J. C , Buchanan 1. T.. Cawel L. J. and Large R. (1992) A comprehensive determination of produced water composition. In Produced Water, cds J. P. Ray and F. R. Engelhart. pp. 97-112. Plenum Press, New York.

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