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 Results and discussion 48
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 Results and discussion 92
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 Results and discussion 136
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.
5.3.3.2 Infusion electrospray ionisation multistage mass 159
spectrometry (ESI-MS°) analysis of the recrystallised product
of the thermal reaction of palmitic acid with
diethylenetriamine in xylene solvent
5.3.3.3 Infusion electrospray ionisation multistage mass 163
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
Table 3.7 Thin layer chromatography Rf values for resolved crude oil and CI-
El imidazoline inhibitor components (TLC 2). Conditions and
procedure described in experimental section 3.2
Table 3.8 Thin layer chromatography Rf values for resolved crude oil and CI-
E l imidazoline inhibitor components (TLC 3). Conditions and
procedure described in Experimental section 3.2
Table 3.9 Thin layer chromatography Rf values for resolved crude oil and CI-
EI imidazoline inhibitor components (TLC 4). Conditions and
procedure described in Experimental section 3.2
Table 3.10 Thin layer chromatography Rf values for resolved crude oil and CI-
EI imidazoline inhibitor components (TLC 5). Conditions and
procedure described in Experimental section 3.2
Table 3.11 Thin layer chromatography Rf values for resolved crude oil and CI-
EI imidazoline inhibitor components (TLC 6). Conditions and
procedure described in Experimental section 3.2
Table 3.12 Thin layer chromatography Rf values for resolved crude oil and Cl-
El imidazoline inhibitor components (TLC 7). Conditions and
Page
28
41
45
45
47
47
50
50
52
52
52
53
53
58
58
72
procedure described in Experimental section 3.2
Table 3.13 Thin layer chromatography Rf values for resolved crude oil and CI- 54
EI imidazoline inhibitor components (TLC 8). Conditions and
procedure described in Experimental section 3.2
Table 3.14 Thin layer chromatography Rf values for resolved crude oil and CI- 54
EI imidazoline inhibitor components (TLC 9). Conditions and
procedure described in Experimental section 3.2
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)
Table 3.19 Peak data determined from HPLC/ESI-MS extracted ion 74
chromatograms of analysis 4 for internal standard 2:1-palmitic
imidazoline spiked into crude oil (extraction SPE 4)
Table 3.20 Peak data determined from HPLC/ESI-MS extracted ion 76
chromatograms of m/z 562.6 (positive ion) for 1 g g"' internal
standard 2:1-PI spiked into crude oil (SPE 5)
Table 3.21 Peak data determined from HPLC/ESI-MS extracted ion 79
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)
Table 3.23 Peak data determined from HPLC/ESI-MS extracted ion 81
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'')
Table 3.24 Peak data determined fi-om HPLC/ESI-MS extracted ion 82
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 ')
Table 3.25 Peak data determined fi-om HPLC/ESI-MS extracted ion 82
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 ^ig 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
[(time/%A) 0/75-0.1/75-17/100; A) 0.1% TFA in methanol and B)
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 ^ig 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 (l^ig 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
^iL 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 ^iL 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 p^aks 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 ^ig 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
[(time/%A) 0/75-0.1/75-17/100; A) 0.1% TFA in methanol and B)
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.
Figure 4.30 HPLC/ESI-MS extracted mass chromatograms of imidazoline 130
corrosion inhibitor product (CI-El); (A) Cisionionoamides and (B)
Ci8:n/Ci8:ndiamides. Conditions as Figure 4.28.
Figure 4.31 HPLC/ESI-MS extracted mass chromatograms of imidazoline 131
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.
Figure 5.2 Total ion (TIC; Top) and base peak (BP; Bottom) HPLC/ESI-MS 140
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).
Figure 5.6 Total ion (TIC; Top) and base peak (BP; Bottom) HPLC/ESI-MS 147
chromatograms of the crude palmitic-diamide product of the solid
phase thermal reaction of palmitic acid with DETA.
Figure 5.7 Total ion (TIC; Top) and base peak (BP; Bottom) HPLC/ESI-MS 148
chromatograms of the recrystallised palmitic-diamide product of the
solid phase thermal reaction of palmitic acid with DETA.
Figure 5.8 Total ion (TIC; Top) and base peak (BP; Bottom) HPLC/ESI-MS 149
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-
monoamide {m/z 342.4), (C) 2:1-PI {m/z 562.6) and (D) palmitic-
diamide {m/z 580.6).
Figure 5.10 HPLC/ESI-MS extracted mass chromatograms from the 151
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).
Figure 5.11 HPLC/ESI-MS extracted mass chromatograms from the 152
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-
monoamide {m/z 342.4), (C) 2:1-PI {m/z 562.6) and (D) 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
fragmentation pathway.
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
AA) in the MS^ spectrum (Figure 5.24).
Figure 5.26 ESI-MS^ CID mass spectrum of the product ion, m/z 562.5 (42 % 171
AA) in the MS^ spectrum (Figure 5.23).
Figure 5.27 ESI-MS** CID mass spectrum of the product ion, m/z 281.3 (53 % 171
AA) in the MS^ spectrum (Figure 5.26).
Figure 5.28 ESI-MS^ CID mass spectrum of the product ion, m/z 282.3 (47 % 172
AA) in the MS^ spectrum (Figure 5.23).
Figure 5.29 ESI-MS^ CID mass spectrum of the product ion, m/z 299.2 (28 % 172
AA) in the MS^ spectrum (Figure 5.23).
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 fi^equency
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 fi^om 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 ^iL 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|iMi^iiiii|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/,W^is(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. Af^er 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 l^orth 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
Mass spectrometry analysis was carried out using a Finnigan Mat LCQ™
(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 ^iL 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 ^iL 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
Analysis 2 Time (min) 0 0.1 15 30 35 40
5|iL injection % A 75 75 95 95 100 100 5|iL injection % B 25 25 5 5 0 0
Analysis 3 Time (min) 0 0.5 11 20 25 30
5|iL injection % A 75 75 95 95 100 100 5|iL injection % B 25 25 5 5 0 0
Analysis 4 Time (min) 0 0.5 11 20 25 30
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
Mass spectrometry analysis 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 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 Results and discussion
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.^eT 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;
Table 3.7 Thin layer chromatography Rf values for resolved crude oil and CI-EI
imidazoline inhibitor components (TLC 2). Conditions and procedure
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 Rf^a 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
Table 3.8 Thin layer chromatography Rf values for resolved crude oil and CI-EI
imidazoline inhibitor components (TLC 3). Conditions and procedure
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
Table 3.9 Thin layer chromatography Rf values for resolved crude oil and CI-EI
imidazoline inhibitor components (TLC 4). Conditions and procedure
described in Experimental section 3.2
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)
Table 3.10 Thin layer chromatography Rf values for resolved crude oil and CI-EI
imidazoline inhibitor components (TLC 5). Conditions and procedure
described in Experimental section 3.2
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
imidazoline inhibitor components (TLC 6). Conditions and procedure
described in Experimental section 3.2
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
imidazoline inhibitor components (TLC 7). Conditions and procedure
described in Experimental section 3.2
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
Table 3.13 Thin layer chromatography Rf values for resolved crude oil and CI-EI
imidazoline inhibitor components (TLC 8). Conditions and procedure
described in Experimental section 3.2
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
imidazoline inhibitor components (TLC 9). Conditions and procedure
described in Experimental section 3.2
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.
^QQ^AvPraypdScan: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?83tt32^i 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 unfi^ictionated 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
Time (min) Peak Area Peak Height Signal to Noise
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.
Table 3.19 Peak data determined from HPLC/ESI-MS extracted ion chromatograms of
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.
Table 3.20 Peak data determined from HPLC/ESI-MS extracted ion chromatograms of
m/z 562.6 (positive ion) for I ng g'* internal standard 2:1-PI spiked into
crude oil (SPE 5)
Extracted ion chromatog rams, m/z 562.6 Analysis Peak Retention
Time (min) Peak Area Peak Height Signal to Noise
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 ^ig 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
Time (min) Peak Area Peak Height Signal to Noise
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
Time (min) Peak Area Peak Height Signal to Noise
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.
Table 3.22 Peak data determined from HPLC/ESI-MS extracted ion chromatograms of
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
Time (min) Peak Area Peak Height Signal to Noise
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)
Peak Area Peak Height Signal to Noise Ratio
Standard 15.68 211266279 6787619 186 81 15.66 51297101 1852033 105
Table 3.23 Peak data determined from HPLC/ESI-MS extracted ion 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 ng mL"')
Extracted ion chromatograms, m/z 562.6 Analysis
1.01 ng mL*' Peak Retention
Time (min) Peak Area Peak Height Signal to Noise
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)
Peak Area Peak Height Signal to Noise Ratio
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
m/z 562.6 and 614.7 (positive ion) for 2:1-PI and 2:1-01 spiked into crude
oil(l.12/10.4 ^gg- )
Extracted ion chromatog rams, m/z 562.6 Analysis Peak Retention
Time (min) Peak Area Peak Height Signal to Noise
Ratio SI 15.17 45322942 1928019 30 S2 15.10 43934279 1938563 53
Extracted ion chromatog rams, m/z 614.7 Analysis Peak Retention
Time (min) Peak Area Peak Height Signal to Noise
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
m/z 562.6 and 614.7 (positive ion) for 2:1-PI and 2:1-01 spiked into crude
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
Time (min) Peak Area Peak Height Signal to Noise
Ratio SI 14.79 20809552 860821 41 S2 14.75 24158678 1001944 44
Extracted ion cbromatog rams, m/z 614.7 Analysis Peak Retention
Time (min) Peak Area Peak Height Signal to Noise
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 ^iL 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 ^iL 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 ^iL 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
4.3 Results and discussion
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
Figure 4.8 HPLC/ESI-MS mass chromatograms of 2:1-oleic imidazoline product by
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 ^iL 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)
Figure 4.10 HPLC/ESI-MS mass chromatograms of 2:1-oleic imidazoline 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
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,^i,
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 ^igmL '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 OOE^OO ^
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)
Figure 4.30 HPLC/ESI-MS extracted mass chromatograms of imidazoline corrosion
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)
Figure 4.31 HPLC/ESI-MS extracted mass chromatograms of imidazoline corrosion
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).
5.3 Results and discussion
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
Figure 5.2 Total ion (TIC; Top) and base peak (BP; Bottom) HPLC/ESI-MS
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
Figure 5.6 Total ion (TIC; Top) and base peak (BP; Bottom) HPLC/ESI-MS
chromatograms of the crude palmitic-diamide product of the solid phase
thermal reaction of palmitic acid with DETA.
147
15.70
§ 40 0.46
15 67
10 Time (min)
15
NL: 7 13E6 Base Peak m/z = 100 0-1000 0
20
Figure 5.7 Total ion (TIC; Top) and base peak (BP; Bottom) HPLC/ESI-MS
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
Figure 5.8 Total ion (TIC; Top) and base peak (BP; Bottom) HPLC/ESI-MS
chromatograms of the recrystallised 2:1-PI product of the solid phase
thermal reaction of palmitic acid with DETA.
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
diethylenetriamine in xylene solvent
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
•^oo-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
fragmentation pathway.
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
diethylenetriamine in xylene solvent
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 ^o--
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
the MS^ spectrum (Figure 5.24).
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
the MS^ spectrum (Figure 5.23).
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
the MS^ spectrum (Figure 5.26).
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
the MS^ spectrum (Figure 5.23).
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
the MS^ spectrum (Figure 5.23).
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 (MS^a; 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 fi^agmentation 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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simulations of oleic imidazolines bound to feme clusters. Journal of Physical
Chemistry A 1997. 101, 83-89.
(124) Silverstein, R. M.; Webster, F. X. Spectrometnc Identification of Organic
Compounds, 6 ed.; John Wiley and Sons, Inc.: New York, 1997.
(125) The Offshore Chemical Regulations 2002,
http://vyww.legislation.hmso.gov.ukysi/si2002/20021355.htm.
(126) Sabeur, Z. A.; Tyler, A. O.; Hockley, M. C. Development of Particle Based
Modelling Concepts for the Simulation of Jet and Plume-like Discharges in the
Marine Environment. Proceedings of the Vth International Conference on
Computational Hydraulics, Computational Mechanics Publications, WIT Press.:
Lisbon, June 2000.
(127) Meier, S.; Andersen, T. E ; Hasselberg, L.; Kjesbu, O. S.; Klungsoyr, J. et al.
Hormonal effects of C 4 - C 7 alkylphenols on cod {Gadus morhua),
http://www.imr.no.
(128) Rowland, S. J. Managment of the Impact of Marine Discharges of Industrial
Chemicals, 2000, Final Report (GST021832) to NERC.
(129) McCormack, P.; Worsfold, P. J.; Gledhill, M. Separation and detection of
siderophores produced by marine bacterioplankton using high performace liquid
chromatography with electrospray ionization mass spectrometry. Analytical
chemistry 2()03, 75, 2647-2652.
209
(130) http://www.svagcn.com.
(131) Robb, D. B.; Covey, T. R.; Bruins, A. P. Atmospheric pressure photoionisation: An ionization method for liquid chromatography-mass spectrometry. Analytical Chemistry 2000. 72, 3653-3659.
(132) Gallagher, R. T.; Balogh, M. P.; Davey, R; Jackson, M. R ; Smclair, I. et al.
Combined electrospray ionization-atmospheric pressure chemical ionization source
for use in high-throughput LC-MS applications. Analytical Chemistry 2003, 75,
973-977.
(133) http://www.europe.appliedbiosvstems.com
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. Bn^om 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
1 I GOO
P24 4
400
138.1
M 100
164.5
RCIVI
tsao.4
I 111) I,' .11 , , 300
1,3 Oiamde
NCOR
.H,0
NCOR
m* 562.5
As per reference 6
Art 95.2
VI t.2DiamiJe COR
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 ser^itive 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
— I — , — .
25
100
50
I X
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NL: 3.44£6
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15.38
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
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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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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^^and [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
Fragment Ion m/z 72.1
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
Fragment Ion m/z 58.1
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.
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