Thermal Desorption Apps for Foods

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Thermal Desorption:

A Practical Applications Guide

IV. Food, Flavour, Fragrance &Odour Profiling

2nd Edition

FFF 2nd edition (Final)_Layout 1 02/06/2010 08:53 Page 1

1

Introduction to Markes International Ltd

Formed in 1997, Markes International is world leader in the

development and manufacture of analytical thermal desorption (TD)

instrumentation and associated sampling equipment for measuring

VOCs and semi-volatiles in air & materials.

Markes has pioneered major TD innovations such as quantitative re-

collection for repeat analysis (SecureTD-Q™), TubeTAG™ RFID tube

labels, DiffLok™ enabling technology for robust tube automation

and cryogen-free analysis of multiple canister air samples. All these

innovations feature in Markes’ well known modular range of TD

instruments: UNITY™, ULTRA™, Air Server™ and the most recent

addition, the TD-100™. Other ground-breaking TD products from

Markes International include the twin-trap TT24-7™ for continuous,

online air monitoring, and unique sampling accessories such as the

Micro-Chamber/Thermal Extractor™ and HS5-TD™ for liquid and

solid samples.

Markes’ TD units can be seamlessly combined with all major brands

of GC and GC/MS to provide trace or high level monitoring solutions.

What is analytical TD?

Analytical thermal desorption is a sample introduction technique for

GC and GC/MS, which uses heat and a flow of inert gas, rather than

an organic solvent, to extract/desorb analytes from the sample

media, delivering them directly to the gas chromatograph. Since the

early 1980s, TD has provided the ultimate versatile sample

introduction technology for GC, by combining selective concentration

enhancement with direct extraction into the carrier gas and efficient

transfer/injection, all in one fully automated and labour-saving

package.

Markes International Ltd, UK headquarters


2

Markes International LtdT: +44 (0)1443 230935 F: +44 (0)1443 231531E: [email protected] W: www.markes.com

Overview

Thermal desorption is now recognised as the technique of choice for

environmental air monitoring and occupational health & safety.

Relevant standard methods include: ISO/EN 16017, EN 14662

(parts 1 & 4), ASTM D6196, US EPA TO-15/17 and NIOSH 2549.

TD is also routinely used for monitoring volatile and semi-volatile

organic compounds (SVOC) in products and materials. Examples

include residual solvents in packaging & pharmaceuticals, materials

emissions testing and food, flavour & fragrance profiling.

This publication presents several real-world applications of TD for

measuring (semi-)volatiles in food, flavour, fragrance and odours.

Accompanying publications cover the applications areas of:

• Residual volatiles & materials emissions testing

• Defence & forensic

• Environmental monitoring and occupational health &

safety

Applications in food, flavour and fragrance

• Fragrance profiling of ingredients in toiletries and

consumer products

• Identification of key olfactory components

• Characterisation/sourcing of natural products

• Odour profiling for potable spirits

• Quantitation of volatile components in dried foodstuffs

• Off-odour/taint analysis

• Biology/crop research

• Flavour profiling of GM foods


3

Background:

In comparison to traditional solvent extraction techniques,

direct thermal desorption (TD) provides a labour-saving way to

extract volatiles from solids, resins, pastes, emulsions and

liquids.

To an analyst, this technique simply involves placing a small

amount of sample directly into an empty TD sample tube or

liner and positioning it on the thermal desorber.

Once the tube is in position, the sample is heated in a stream

of inert gas. The volatiles are swept out and pre-concentrated

on the focusing trap leaving the matrix behind. The focusing

trap is subsequently desorbed and vapours are transfered

(injected) into the GC(MS) analytical system.

Direct TD also facilitates selective concentration of extracted

compounds. Focusing trap parameters can be selected to allow

water and/or other solvents to be purged to vent, thus

minimising interference, meaning only components of interest

are transferred.

Direct desorption is used for both:

• Complete (exhaustive) extraction (e.g. for packaging)

• Characterisation of materials using a representative vapour

profile

The horizontal orientation of sample tubes in

Markes Series 2 UNITY & TD-100 systems

minimises the risk of samples shifting

within the tube or falling out.

Samples can be weighed directly into glass, steel or Silcosteel® tubes, or into

disposable, PTFE-based tube inserts/liners. Pastes, resins, liquids &

emulsions can also be accommodated using tube liners containing plugs of

glass or quartz wool.

Odour profiling by direct thermal desorption/

extraction


4


Background:

Detailed analysis of natural oils (such as sesame oil) may

be required e.g. to identify key olfactory components, to

characterise & source the material, or to identify oxidation

products/other potential causes of taint. Traditionally, this

application has been carried out using multi-step liquid

extraction or steam distillation with GC/MS analysis,

however such procedures are long, manual & inefficient.

Direct thermal desorption provides a simple & readily

automated alternative.

Markes TD instrumentation is uniquely well-adapted for

aroma/taint identification because the short, inert flow path

can be set at temperatures low enough to ensure recovery

of most reactive GC-compatible olfactory components.

Direct thermal desorption/extraction can be achieved using

either an empty TD tube or the Markes µ-CTE (p 27),

followed by TD-GC/MS analysis.

Typical analytical conditions:

Sampling: A few mg oil loaded onto a glass wool plug behind

1 cm bed of Tenax TA in a glass TD tube, or a few mL oil

incubated in a µ-CTE chamber at 80-100ºC with vapour

collection on a Tenax TA tube (gas flow ~100 mL/min)

TD system: Series 2 UNITY or TD-100

Desorption: 10 mins at 300ºC

Cold trap: U-T9TNX-2S (Tenax TA)

Split ratio: >100:1

Analysis: GC/MS

Profiling natural oils by direct desorption

Direct desorption of sesame oil sample

7.5 mg sesame oil

Empty tube showing system background

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5

Profiling volatiles in dried foodstuffs by direct

desorptionBackground:

Equilibrium headspace sampling of dried foods generally

requires solvent addition and does not allow the analysis of

a wide range of volatiles. Using Markes’ TD instrumentation

for direct desorption of homogenous dried foods provides a

high sensitivity & labour-saving alternative, which permits

the analysis of a wider volatility range. Foodstuffs

compatible with this approach include:

• Ground spices

• Freeze-dried products, such as ground or instant coffee

• Animal feed pellets

Proprietary valve technology makes Markes TD systems

compatible with the widest possible analyte range (C2 to n-

C40 and reative species) all on one platform.


Sampling: 100–200 mg weighed into empty glass tube or

PTFE liner

TD system: UNITY 2 or TD-100


Trap: Quartz wool/Tenax TA

Split: ~25:1 split during trap desorption only

Analysis: GC/MS

Reference: TDTS 23 (Utilising the UNITY method development

mode to analyse dried foodstuffs)

Direct desorption of ground dried animal-feed pellets weighed into an empty

glass tube

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6


“High/low” analysis of trace & high-level aroma

constituents using SecureTD-QBackground:

Markes TD systems have an inert flow path that can be set

at low temperatures, which makes them ideal for the direct

desorption of labile volatiles such as terpenes and sulphur

compounds. SecureTD-Q (i.e. quantitative re-collection of

split flow) facilitates repeat analysis of a sample under the

same or different conditions (e.g. at a lower split setting, as

shown) to confirm quantitative recovery of reative

components through the system & to allow detailed analysis

of trace constituents.

Quantitive re-collection & repeat analysis under different

split conditions can extend the TD-GC/MS dynamic range to

5 or 6 orders of magnitude offering “high/low” capability.

This is a significant advantage for many flavour/fragrance

applications


Sampling: ~100 mg of leaf sample weighed into an empty

glass tube or PTFE liner secured with quartz wool

Re-collection on Tenax TA/UniCarb™ Silcosteel



Trap: U-T6SUL-2S (Sulphur trap)

Flow path: 80ºC to 150ºC depending on target compounds

Split: ~25:1 and repeat analysis at 5:1 split

Analysis: GC/MS

Vapours extracted from a leaf sample. Direct desorption (blue) followed by

repeat analysis of re-collected sample (black) with lower split ratio to enhance

sensitivity for trace components

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Markes TD valve allows quantitative

re-collection of split flow (SecureTD-Q)


7

Background:

Mushroom powder can be used in cooking as a flavour

substitute for whole mushrooms. It is dry, relatively

homogeneous & can be conveniently analysed by direct TD-

GC/MS without manual sample preparation. However, the

analysis of such powders is challenging because of the

large range of concentrations of the constituents.

The quantitative re-collection for repeat analysis

(SecureTD-Q) ability of every Markes TD system uniquely

accomodates this wide dynamic range with re-analysis

under differing conditions; a high split analysis to measure

major consituents is typically followed by repeat analysis

under low split conditions to identify trace components.


Sampling: Direct desorption of ~50 mg mushroom powder

in a glass tube



Trap: U-T15ATA-2S

Trap conditions: 0ºC to 300ºC for 5 mins

Split: 25:1

Analysis: GC/MS

Flavour profiling of mushroom powder via direct

desorption

1 Acetaldehyde

2 Ethanol

3 Butanal

4 Hexanal

5 Heptanal

6 D-Limonene

7 Octanal

8 Nonanal

9 Acetic acid

10 Benzaldehyde

11 Propylene glycol

12 Butyrolactone

13 Butanoic acid

14 Phenylmethyl ester acetic acid

15 2-Methyl-, 1-(1,1-dimethylethyl)-2-

methyl-1,3-propanediyl ester

propanoic acid

16 Phenol

17 2-Pyrrolidinone

18 2-Phenoxy-ethanol

19 Caprolactam

20 Methyl dihydrojasmonate

21 2,4-Di-tert-butylphenol

22 1-Hexadecanol

23 Benzophenone

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8


Background:

The development of new crop species (e.g. genetic

modification to aid pest resistance or to boost growth in arid

areas) requires testing of the flavour profile to make sure it

is enhanced, or at least remains acceptable, in the new

variety.

In the case of bulk, inhomogeneous materials like fresh

fruit/vegetables, flavour profiles are best obtained by

purging headspace volatiles from large (~1 kg) samples,

cooked or raw, & collecting the vapours on tubes packed

with Tenax TA. Tenax TA is completely hydrophobic so almost

all water passes straight through during the vapour

sampling process, simplifying profile interpretation.

Pioneered by Markes, SecureTD-Q offers quantitative re-

collection of any split flow for repeat analysis & confirmation

of analyte recovery. SecureTD-Q is standard on every

Markes TD system (contact Markes for futher details).


Sampling: 50 mL/min for 20 mins

TD system: Series 2 ULTRA-UNITY or TD-100

Prepurge: 3 mins (to trap and split)


Trap: U-T9TNX-2S (Tenax TA)

Split flow: 20 mL/min

Analysis: GC/MS

Flavour profiling new crop varieties by sampling

vapours onto sorbent tubes

Volatiles from boiling potatoes sampled using Tenax tubes & analysed using

TD-GC/MS with SecureTD-Q: Original sample (black) and re-collected sample

(red). Identical chromatographic profiles confirm quantitative recovery of labile

analytes (e.g. terpenoids)

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Original

Reference: TDTS 24 (SecureTD-Q™ -

Re-collection for repeat analysis) & 84

(Using thermal desorption to enhance

aroma profiling by GC/MS)


9

Background:

Complex GC/MS data can be compromised by interference

(noise) which can make interpretation difficult. New

software has been developed to address this.

ClearView™ is one of a suite of state-of-the-art GC/MS data

reprocessing packages from ALMSCO International,

available from Markes. It uses a sophisticated algorithm to

accurately and dynamically compensate for

chromatographic background as it changes throughout a

run. Key advantages include:

• Reduced signal to noise for improved

sensitivity/detection

• Improved spectral purity which improves automatic

identification of trace components

ClearView produces a second reprocessed data file for each

analysis (see example opposite)


Sampling: Vapours from a burning incense stick were

collected onto Tenax TA/UniCarb™ tube over 5 min using

the MTS-32 (p. 36)

TD system: Series 2 UNITY

Primary desorbtion: 10 min at 300ºC

Split: 15:1

Trap: T6-SUL-2S (sulphur trap)

Trap conditions: -10ºC to 300ºC, 5 min

Analysis: GC/MS

Removing background interference with

ClearView™: An example with incense

ClearView™

References: TDTS 83 & 85 (Using ClearView reprocessing to

enhance trace GC/MS analysis)

Original data

ClearView reprocessed data

Vapour analysis from a lit incense stick. Original data (top) and ClearView

reprocessed data (bottom)


10


Identifying trace target compounds using

TargetView™: An example with potato crisps (chips)

TargetView builds upon the foundation of ClearView. It is a

sophisticated GC/MS datamining package, offering automatic

interpretation of complex chemical profiles. TargetView facilitates the

detection and measurement of target compounds even if they are at

trace levels and co-eluting with other compounds. Original data files

are left intact and unaffected, so operation of TargetView is risk-free.

It works as follows:

1. Dynamic background compensation (ClearView) is applied

to eliminate interferences such as column bleed.

2. The GC/MS data (total ion chromatogram [TIC]) of the

sample is deconvoluted & ‘principal component analysis’

identifies targets using a selected library of compounds.

3. Target compounds found are assigned a match co-efficient,

depending on the correlation between sample & library

spectra.

4. A report listing all identified target compounds and

associated peak areas is produced.

5. A plot of the TIC with compounds represented by red bars

(the HPlot) may also be displayed.

Above: Enlarged view of potato crisp profile with

automatic detection of target peaks (HPlot: red bars).

Right: Highlighted peak shows dimethyl pyrazine (*)

co-eluting with multiple non-target compounds

Automated post-run report displaying target hits

*


11

SPE-tD™ cartridges

Markes SPE-tD cartridges offer a simple, convenient method for

sampling less volatile impurities in aqueous samples. Such

applications would otherwise require manually-intensive extraction or

distillation techniques before GC(MS) analysis.

SPE-tD cartridges are hollow and coated inside and out with

polydimethyl siloxane (PDMS) for optimum capacity. The cartridge is

placed into an aqueous sample and agitated. Volatile and semi-

volatile organics in the sample partition between the aqueous matrix

and PDMS, reaching equilibrium over time. This allows semi-

quantitative analysis of less volatile organics and direct comparison

of organic impurity levels in two similar samples.

After equilibration, the SPE-tD cartridge is removed from the sample,

rinsed in pure water to remove solid residues (if necessary) and

placed into an empty TD tube. The cartridge is then dry purged with

pure carrier gas, on- or offline, prior to analysis by TD-GC/MS.

Sorptive extraction/TD methods provide a complementary sample

preparation tool to automated headspace (HS) and purge-and-trap

(P&T) techniques, which favour volatiles. The use of SPE-tD

cartridges in combination with HS or P&T allows full characterisation

of aqueous samples; volatile & semi-volatile constituents.

Key Applications include:

• Off-odours/taints in drinking water

• Semi-volatiles in processed fruit juices

• Profiling of hydrosols (aqueous fraction from steam

distillation of natural oils).


Background:

High capacity sorptive extraction using Markes’ SPE-tD

cartridges provides a convenient approach to monitoring

semi-volatile off-odour components in drinking water. SPE-tD

cartridges used in combination with subsequent high

sensitivity TD-GC/MS analysis offer selective concentration

of less volatile constituents & trace-level detection limits

(sub-ppb). This complements purge-&-trap/equilibrium

headspace methods for volatiles.

The example opposite shows sub-ppb impurities absorbed

by a SPE-tD cartridge from a 1 L sample of drinking water.


Sampling: SPE-tD cartridge placed into 1 L water sample

and agitated for 2 hours


Desorption: 60ºC for 10 mins

Trap: U-T2GPH-2S (General purpose hydrophobic)

Trap Conditions: 30ºC to 300ºC

Split flow: 10 mL/min during trap desorption

Analysis: GC/MS

Reference: TDTS 88: (Using SPE-tD for profiling flavour &

fragrance compounds of fruit juices & wine)

Profile of sub-ppb level organics extracted from drinking water using the

SPE-tD cartridge

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Extraction of odourous organics from drinking water

using SPE-tD

12



13

Coupling headspace with thermal desorption (HS-TD)

Markes’ HS5-TD module for UNITY 2 brings together two of the most

powerful GC introduction techniques: Headspace (HS) sampling and

thermal desorption (TD).

HS5 accomodates up to five (5) standard

(~20 mL) headpsace vials in a common

headed zone with manual vial selection.

The inert needle, used for vial

pressurisation and HS vapour sampling,

is lowered into the vial using a

convenient user-operated lever. A heated

tower protects the needle and eliminates

cold spots.

HS vapours from the pressurised vial pass through the needle and

directly into the cryogen-free focusing trap of UNITY 2, allowing

efficient concentration of the compounds of interest. Water and

other unwanted volatiles are selectivley purged to vent, allowing high

sensitivity capillary GC(MS) analysis with minimal interference.

The combined series 2 UNITY–HS5 system offers optimum

sensitivity for trace-level organics in solid, liquid and vapour-phase

samples, all on one versatile analytical platform.

The series 2 UNITY–HS5 system can operate in two modes:

• Headspace trap

• Thermal desorption of sorbent or sample tubes

The combination of multi-stage headspace trapping and highly

efficient trap desorption/GC injection offers maximum sensitivity;

ideal for drinking water analysis and other trace-level applications.

Repeated pressurisation and evacuation of headspace vials also

extends the analyte volatility range, allowing higher boiling

compounds to be recovered and

measured simultaneously with volatiles.


14


Background:

Drinking water is prone to contamination by naturally

occurring odorous compounds such as geosmin, methyl-i-

borneol and trihaloanisoles. These components produce a

musty/’earthy’ smell that is detectable by consumers at

concentration levels down to 10 ppt.

HS-TD offers a simple, innovative and readily-automated

approach to routine analysis of odorants in drinking water.

Detection limits down to 1 ppt can be achieved using

conventional 20 mL HS vials/caps and GC/MS.

Eradicating the chromatographic effects of water or other

background interference using ClearView reprocessing

software, optimises signal-to-noise (sensitivity) at the lowest

levels.


TD system: HS5-UNITY 2

HS vials: 45-50ºC; Sample cycles: 10

Trap: U-T2GPH-2S (General purpose)

Trap conditions: Held at 30ºC (purgeables), and 50ºC

(odorants)

Desorption: 300ºC for 5 min

Analysis: GC/MS

References: TDTS 78 (Low ppt-levels of odorants in drinking

water using HS-TD), TDTS 83 & TDTS 85 (ClearView)

Low-ppt level odorants in drinking water using HS-TD

Without ClearView data reprocessing

With ClearView data reprocessing

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5 ppt level odorants in drinking water analysed by HS-TD-GC/MS shown with

and without ClearView reprocessing


15

Background:

A variety of compounds define the aroma and flavour of fruit

juices. The analyses of flavour compounds in these types of

beverage usually require cumbersome sample preparation

steps such as liquid/liquid extraction, solid-phase extraction

or distillation, often with the drawback of organic solvent

use.

Markes UNITY 2-HS5 system can be used in HS-TD mode to

characterise compounds that contribute to the aroma of a

sample. It can also be used to desorb SPE-tD cartidges

allowing flavour compounds to be analysed without the

need for solvent extraction, & on the same analytical

platform.


Sampling: 20 mL sample in sealed vial at ambient

temperature (HS5), & 20 mL sample in sealed vial at

ambient temp. with cartridge & stirred for 1 hour (SPE-tD)

TD system: Series 2 UNITY-HS5

Sampling mode: Dynamic headspace for 3 mins (HS5), &

tube desorption at 180°C for 5 mins (SPE-tD)

Trap: U-T2GPC-2S (General purpose hydrophobic)


Split flow: 20 mL/min during

trap desorption only

Analysis: GC/MS

TD-GC/MS of freshly squeezed orange juice sample. HS (black) & SPE-tD

cartridge (red)

Reference: TDTS 88 (Enhancing olfactory profiling of fruit juices

and wine using complementary analytical thermal desorption

techniques)

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HS5-TD and SPE-tD of fruit juice


16


Background:

Wine aroma comprises a complex mixture of organic

volatiles, mainly terpenes and C13-norisoprenoids, which

supply ‘fruity’ or ‘floral’ notes. The highest volatility

compounds are monitored best by HS-TD, and the

combination of this technique with SPE-tD (targeted at lower

volatility components) ensures a broad range of compounds

are seen.

Brettanomyces (Dekkera) bruxellensis (‘Brett’), a spoilage

yeast found in beer and wine, creates off-odours. In this

study, trace levels of several Brett by-products, including the

primary ones of 4-ethyl phenol and 4-ethyl-2-methoxy

phenol, were detected, suggesting Brett contamination.


Sampling: 20 mL sample placed in sealed vial at ambient

temperature (HS5), & 20 mL sample placed in sealed vial at

ambient temperature with cartridge & stirred for 1 hour

(SPE-tD)


Sampling mode: Dynamic headspace for 3 mins (HS5), and

tube desorption at 180ºC for 5 mins (SPE-tD)



Split flow: 20 mL/min during trap desorption only

Analysis: GC/MS

Reference: TDTS 88 (Enhancing olfactory

profiling of fruit juices and wine using

complementary analytical thermal

desorption techniques)

Red wine analysis: HS5-TD and SPE-tD

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Expanded view

Two chromatograms comparing the SPE-tD-GC/MS analysis (red) and HS-TD-

GC/MS analysis (black) of red wine


17

Background:

Markes thermal desorption facilitates detailed analysis of

the flavour profile of potable spirits by allowing selective

elimination of water and ethanol. By doing this, key olfactory

components (ketones, esters, essential oils, etc.), which

would have otherwise been masked, are visible.

Headspace vapours are pumped/purged onto a Tenax TA

trap or tube under conditions which concentrate the target

analytes, whilst allowing most of the water, ethanol and

other very volatile polar components to break through. An

example of whisky analysis, with selective elimination of

water & ethanol, is shown opposite. Selective concentration

of key olfactory components simplifies meaningful odour

profiling.


TD system: UNITY 2 with HS5 module or Direct Inlet

Accessory (p. 19)

Sampling: Sample placed in headspace vial at ~40ºC.

Pulsed mode - 6 headspace extractions

Trap: U-T9TNX-2S (Tenax TA) from -10ºC to 280ºC, backflush

desorption

Analysis: GC/MS

Reference: TDTS 84 (Using TD to enhance aroma profiling by

GC/MS)

Typical VOC profile from whisky headspace with selective elimination of water

& ethanol. Dotted (red) line shows how the ethanol peak would mask key

aroma compounds if not selectively purged from the trap prior to desorption

Whisky

Whisky: Enhanced aroma profiling by HS-TD with

selective concentration


18


Background:

Beer is made mainly from natural products, e.g. malt and

hops, and therefore comprises a vast dynamic range of

volatiles. Flavour compounds, however, can have very low

olfactory thresholds (ppt) and their presence may be at

trace-level. In order to efficiently extract the widest range of

analytes, sorptive extraction using SPE-tD cartidges provides

an easy yet sensitive technique.

Further sample concentration in the focusing trap of the

thermal desorber makes sub-ppt detection possible.

The example opposite shows a close-up of the total ion

chromatogram (TIC) of a beer sample obtained using

sorptive extraction and TD-GC/MS analysis. The complexity

of the profile is an indication of the efficiency of SPE-tD.


Sampling: SPE-tD cartridge placed into 20 mL beer & stirred

for 30 mins


Desorption: 180ºC for 5 min

Trap: U-T15ATA-2S (Air toxics analyser)

Trap high: 200ºC

Split: 20 mL/min

Analysis: GC/TOF-MS

Reference: ALMSCO International application note, ANBT10

Extraction of volatiles from beer using SPE-tD with

subsequent analysis by TD-GC/MS


19

Multi-purpose Direct Inlet Accessory: Direct

sampling/concentration of headspace vapours

The multi-purpose Direct Inlet

Accessory (U-INLET) can be added

to UNITY 2 to provide a simple and

convenient mechanism for

concentration of headspace

vapours from a wide range of bulk

sample containers.

This online approach allows

vapours to be either pumped or

swept continuously through an inert, heated sampling line, directly

into the electrically-cooled focusing trap of UNITY 2, without the

need for a sorbent tube.

The series 2 UNITY-Direct Inlet system has significantly improved

sensitivity over conventional static headspace methods by allowing

multi-stage extraction and concentration before analysis. The

dynamic headspace approach also eliminates the need for

equilibrium to be reached, thus reducing the time required for

analysis.

Sample vessel

The series 2 UNITY-Direct Inlet system is compatible with a wide

range of sample vessels. It may be used for purging headspace

vapours from small, sealed containers (such as reaction vessels or

headspace vials) or for pumping air from open or compressible

containers such as bell jars or Tedlar® bags.

Key application areas include:

• Characterisation of VOC profiles from natural products

and manufactured goods

• Monitoring emissions from living organisms, e.g. plants,

microbes, fungi, insects, etc., over time

• Monitoring malodours generated from food packaging

(e.g. drink bottles)

• Off-odour/shelf-life testing

• Sampling from drinks/spirits, with the option of

selectively purging the ethanol (see p. 17)

UN

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Optional pump

Gas/air inlet


20


Background:

Cow’s milk is an important source of nutrition. Milk

production cannot be isolated from the environment and is

therefore subjected to potential contamination by VOCs

present in the air and from the food and water consumed

by cows.

Markes series 2 UNITY-Direct Inlet system has been utilised

for the analysis of VOCs in the headspace of whole milk at

room temperature.


Sampling: Individual milk samples of ~150 mL placed in

sealed vials at ambient temperature

TD system: Series 2 UNITY-Direct Inlet Accessory

Headspace sampling: 10 mins

Cold trap: U-T9TNX-2S (Tenax TA trap)


Split flow: 20 mL/min during trap desorption only

Analysis: GC/MS

Three replicate fresh whole milk headspace analyses at room temperature

1 Acetone

2 Pentanal

3 Toluene

4 Butanoic acid

5 Hexanal

6 2-Pentanone, 4-hydroxy, 4-

methyl

7 Xylene

8 2-Heptanone

9 Nonane

10 Heptanal

11 Decane

12 Octanal

13 Limonene

14 Undecane

15 Nonanal

16 2-Ethyl hexanoic acid

17 Dodecane

18 Decanal

19 Tridecane

20 Tetradecane

21 Pentadecane

22 Tetradecanoic acid

23 Pentadecanoic acid

24 Hexadecenoic acid

25 Hexadecanoic acid

26 Octadecenoic acid

27 Octadecanoic acid

28 Cholesta-3,5-diene

VOCs in milk samples by bulk HS-TD


21

Background:

Product taint can be introduced via:

• Odorous base materials

• Issues with the fragrance additives

• Packaging – everything from printed film to wood pallets

• Warehouse storage

Markes provides a comprehensive toolkit for tracking down

the sources of taint; Direct TD (dynamic headspace [HS]) of

sample in empty sample tubes; thermal extraction/HS of

larger samples using µ-CTE (p. 27); HS-TD (p. 13); sampling

larger volumes of HS vapour using the direct inlet accessory

(p. 19) & on- or offline vapour sampling for air/gas

characterisation e.g. warehouse air or process CO2 purity.

Typical analytical conditions (for direct desorption of PET):

Sampling: 200 mg of ground polymer in an empty tube



Trap: U-T6SUL-2S (Sulphur trap)

Trap conditions: -10ºC to 300ºC

Split: 40 mL/min during trap desorption

Analysis: GC/MS

References: TDTS 9, TDTS 40 & TDTS 92

Direct desorption of ground polyethylene terephthalate (PET) polymer to

identify trace level VOCs contributing to taint. Comparison of PET polymers

used in the manufacture of soft drinks bottles

Sample AAce

tald

eh

yde

Sample B

Sample C

Sample D

1,3

-dio

xola

ne

Eth

yle

ne

gly

co

l

Taint & off-odour: Monitoring residual volatiles in

packaging by direct desorption


22


Background:

Markes offers complementary techniques for the

identification of VOCs that may cause taint when present in

food packaging. In this example, TD was used to analyse

printed biscuit wrappers in two ways:

• Direct desorption of the wrapper

• Desorption of Tenax TA tubes onto which HS vapours

from the wrapper were collected

Volatiles from the packaging sample include solvents which

can migrate into fatty foodstuffs, adversely affecting the

taste.


Sample: 10 x 5 cm piece of film, rolled and inserted into an

empty stainless steel tube for direct desorption, & 250 mL

sample of headspace vapour drawn into a Tenax TA sorbent

tube


Desorption: 10 mins at 60ºC (direct TD) and 10 mins at

300ºC (HS sample on Tenax TA tube)

Trap: U-T12ME-2S (Material emissions trap)

Split: 30:1 during trap desorption

Analysis: GC/MS

References: TDTS 9 (Monitoring materials & processes for

VOCs at high and trace Levels) & TDTS 92 (Residual monomer

in polymer by direct desorption)

Direct desorption (red) and headspace analysis (blue) of printed packaging

film. Note the wider volatility range of analytes observed in the direct

desorption run.

1-p

rop

an

ol

Eth

yl a

ce

tate

Pentamethyl heptane

Pe

nta

no

ic a

cid

2,2

,4-t

rim

eth

yl-3

-

ca

rbo

xyis

op

rop

yl,

iso

bu

tyl

este

r

Eth

yl a

ce

tate

Direct desorption

Headspace

vapours

Packaging analysis via direct desorption & sampling

bulk headspace vapours


23

Background:

Thermal desorption is used extensively to monitor odours

associated with meat processing; for example,

environmental/ambient-odour monitoring, product

quality/flavour assessment, testing of animal odours

(healthy and diseased) and monitoring of production

processes.

Meat-related odours often contain reactive species such as

thiols (mercaptans), fatty acids & volatiles amines. The

inertness & adjustable flow path temperature of Markes TD

systems make them ideally suited to this application.

Cryogen-free, sorbent-based analyte trapping also allows

high sensitivity splitless operation, but without the risk of

ice blockage during the analysis of humid samples.


Sampling: 0.5-2 L vapour sampled onto Tenax TA/

Carbograph 1TD tubes


Desorption: 300ºC for 5 mins then 320ºC for 5 mins


Trap conditions: 20ºC to 300ºC

Split: Low split during trap desorption only

Analysis: GC/MS

α-p

ine

ne

3-h

ydro

xy-2

-bu

tan

on

e

Ace

tic a

cid

2-M

eth

yl p

rop

an

oic

acid B

uta

no

ic a

cid

Pe

na

tan

oic

acid

He

xan

oic

acid

4-m

eth

yl p

he

no

l

He

xad

eca

no

ic a

cid

1,5

-pe

nta

ne

dia

min

e

1-h

exa

na

min

e

Bu

tan

am

ide

Concentrating odours from meat processing using

sorbent tubes

Chromatogram of odours from a swine facility. Reproduced with the kind

permission of APS Adamsen, LugTek, Denmark - experts in odours from

livestock production


24


Background:

A recent, high-profile example of taint was linked to 2,4,6-

trichloroanisole (TCA) in wine. TCA is produced from

trichlorophenol by a micro-organism that thrives in the

production process of corks. This, and other chemically

similar analytes, gives the wine a mushroomy ‘corked’

aroma even at low concentrations (<5 ng/L).

The inert flow path & desorption efficiency (sensitivity) of

Markes TD systems readily facilitate TCA measurement in

the headspace of aqueous samples at sub-ng/L levels.

Direct thermal extraction of whole corks to obtain the

overall VOC profile is possible using the Markes µ-CTE (p. 27).


Sampling: On- or offline sampling of headspace from 1 L

aqueous samples at 60ºC onto Tenax TA trap. Whole cork

incubated at 60ºC using µ-CTE with 70 mL/min flow of

helium for 10 mins





Split flow: 30 mL/min

Analysis: GC/MS or GC-olfactometry

TD analysis of 0.2 ng/L TCA and other odour

compounds in the headspace of a 1 L aqueous

sample. (Inset: Vapour profile from whole cork

using µ-CTE)

2,4

,6-t

rich

loro

an

iso

le

Ge

osm

in

2,3

,4-t

rich

loro

an

iso

le

Trib

rom

oa

nis

ole

Thermal extraction of cork using µ-CTE

Trichloroanisoles in wine


25

Background:

Thermal desorption has extensive uses in the tobacco

industry. Key applications include:

• Analysis of environmental tobacco smoke (ETS)

• Aroma profiling of tobacco/tobacco-substitutes

• Monitoring filter efficiency by collecting vapours from

smoking machines (see opposite)

• Tracking the cause of taint in batches of tobacco

products

These applications are carried out using sorbent tube

sampling, direct TD or using accessories such as the µ-CTE

(p. 27).


Sampling: Multiple ‘puff’ volumes taken into bag then

transferred onto sorbent tube, or vapours sampled directly

onto tube



Trap: U-T2GPH-2S (General purpose hydrophobic), 30ºC to

300ºC for 3 mins


Analysis: GC/MS

Reference: TDTS 84 (Applications of thermal desorption in the

tobacco industry)

Testing filter efficiency: VOC profile of tobacco smoke drawn through a

cigarette filter using a smoking machine. Note: smokers are exposed to

volatile aromatics, including benzene, and nicotine (see also p. 37)

Iso

pre

ne

Be

nze

ne

Tolu

en

e

Reproduced with the kind permission of British American Tobacco, UK

Applications for thermal desorption in the tobacco

industry


26


Background:

The tobacco industry began to invest in TD-GC/MS in the

early 1980s for monitoring trace levels of nicotine & other

target compounds in the environment.The new technology

was quickly adopted by product development & QC depts for

fingerprinting/characterising tobacco & other raw materials

& end products.

Markes’ specialist sampling & analytical products provide a

unique combination of flexibility, performance & throughput

to meet the needs of industry. Highlights include:

• Comprehensive range of sample introduction options

• Reliable/high performance analytical TD technology

• Sophisticated GC/MS data reprocessing software


Sampling: Indian tobacco and tobacco from a UK cigarette

(0.5 g) weighed into a 20 mL glass headspace vial. The vial

was sealed & equilibrated for 10 mins at 75ºC



Trap conditions: -10ºC to 320ºC for 5 mins

Split: 20 mL/min during trap desorption only

Analysis: GC/MS

Reference: TDTS 76 (Comparison of tobacco by

headspace–thermal desorption (HS–TD)

Compounds found in Indian and UK tobacco samples

1 Acetaldehyde*

2 Trimethyl amine

3 Ethanol*

4 Acetone*

5 IPA

6 DMS

7 2-Methyl propanal*

8 Methacrolein*

9 2,3-Butanedione*

10 2-Butanone*

11 2-Methyl furan*

12 Ethyl acetate

13 3-Methyl butanal*

14 1-Butanol*

15 2-Methyl butanal

16 Pentanal*

17 Propylene glycol*

18 1-Ethoxy-2-propanol

19 Hexanal*

20 Methyl pyrazine

21 3-Furanmethanol

22 1-(1-3-Dioxolan-2-yl)-

2-propanone

23 2-Acetate 1,2-

propanediol*

24 2,6- Dimethyl

pyridine

25 Benzaldehyde *

26 6-Methyl-5-hepten-2-

one

27 Beta myrcene

28 3,7-Dimethyl-(Z)-

1,3,6-octatriene*

29 Limonene*

30 Cis-linalool oxide

Odour Description:

Sweet Earthy Floral

Spice Lavender*

31 3,7-Dimethyl-1,6-

octadien-3-ol

Olfactive Note:

floral, herbal woody,

rosewood*

32 Pyrrolidine*

33 3,7-Dimethyl-(r)-6-

octen-1-ol Used in

perfumery as a

source of floral

odors*

34 3,7-Dimethyl-1,6-

ocatdien-3-ol

acetate Odour

Description:

Pleasant, sweet,

floral, fruity*

35 1-Acetoxymethyl-3-

isopropenyl-2-methyl

–cyclopentane*

36 3,7-Dimethyl -

acetate (Z)-

2,6,octadien-1-ol It

has a rose-like

odour*

37 2-(3,3-

Dimethylcyclohexylid

ene)-(Z)-Ethanol *

38 Nicotine*

Headspace-thermal desorption analysis of tobacco

UK cigarette sample

Indian tobacco sample


27

Micro-Chamber/Thermal Extractor (µ-CTE)

The µ-CTE is a convenient tool for

monitoring vapour profiles

and emissions from a wide

sample range. Samples

may be tested at near

ambient and elevated

temperatures.

The µ-CTE is available in two formats, configured to suit particular

applications. The M-CTE120 (above left), which can be heated to

120ºC, comprises six (6) micro-chambers each with a volume of 44

cm3 into which samples are placed; the M-CTE250 (above right),

which can be heated to 250ºC comprises four (4) micro-chambers

each with a volume of 114 cm3.

A controlled flow of air or carrier gas is purged through all of the

chambers simultaneously, sweeping the volatiles onto sorbent tubes

which are attached to each chamber lid.

Both formats of the µ-CTE are available with stainless steel or

Silcosteel chambers. These chambers are convenient for samples

which are too inhomogeneous for direct desorption in empty tubes.

Accessories are available to facilitate surface emissions testing and

permeation studies (e.g. of packaging) as well as the volatile

analysis of bulk samples.

Key applications include:

• Bulk sampling of volatiles from fruits, vegetables and

other inhomogeneous foodstuffs

• Fragrance profiling of tobacco blends/substitutes

• Permeation testing of packaging

• Fragrance profiles from consumer products


28


Vapour profiles from ‘rolling’ tobacco (top) and manufactured cigarette

tobacco (bottom), collected on Tenax tubes using a micro-chamber at 50ºC

Background:

The Markes µ-CTE provides an ideal sampling accessory for

inhomogeneous materials such as tobacco. Crumbled

tobacco samples can be placed in Silcosteel micro-

chambers, incubated at user selected temperatures &

purged with air or inert carrier gas to sweep volatiles onto

inert sorbent tubes. Subsequent analysis is via TD-GC/MS.

The chromatograms opposite show comparative odour

profiles from two types of tobacco.

The µ-CTE is exclusively available from Markes. It is similarly

convenient for sampling whole cigarette filters (before or

after smoking), cigarette paper and cigarette packaging

materials.


Sampling: 1 g of tobacco incubated in the µ-CTE at 50ºC.

Vapours swept onto Silcosteel Tenax TA tubes in a 100

mL/min flow of helium for 10 mins





Split: Double split, 300:1

Analysis: GC/MS

Reference: TDTS 84 (Applications of

thermal desorption in the tobacco

industry)

Triacetin

Acetic a

cid

3-(

1-m

eth

yl-

2-

pyrr

olidin

yl)

-pyridin

e

Pro

pyle

ne g

lycol

2,6

,6-t

rim

eth

yl-

bic

yclo

hepta

ne

Buty

rola

cto

ne

VOCs from ‘rolling’ tobacco

VOCs from manufactured cigarette tobacco

Monitoring the aroma/flavour profile of tobacco

using the Micro-Chamber/Thermal Extractor


29

Background:

Milk and related dairy products have a complex aroma

profile comprising fatty acids, lactones, ketones, aldehydes,

esters and hydrocarbons.

Several mL of milk or yoghurt can be conveniently

measured into stainless or Silcosteel micro-chambers and

incubated at temperatures between ambient and 80ºC

under a flow of pure air or inert carrier gas. Emitted vapours

are collected on Tenax TA tubes connected to the exhaust of

each micro-chamber. Water is selectively eliminated.

Note that the inert flow path & cryogen-free operation of

Markes thermal desorption system ensures compatibility

with humid samples and reactive polar analytes


Sampling: 10 mL (g) yoghurt incubated at 70ºC in the

µ-CTE, swept onto Tenax TA tubes in a 70 mL/min flow of

helium for 10 mins






Analysis: GC/MS

Flavour profile obtained from natural greek yoghurt using Markes µ-CTE at 70ºC

He

pta

no

ne

n-C

9

Th

iop

he

no

ne

He

pta

na

l Octa

na

l

Eth

ylh

exa

no

l

Lim

on

en

e

2-n

on

an

on

e

No

na

na

l

De

ca

na

l

Un

de

ca

na

l

Flavour profiling of dairy products using the Micro-

Chamber/Thermal Extractor


30


Flavour profiling of cheese using the Micro-

Chamber/Thermal ExtractorBackground:

There is extensive research into the complex aroma profiles

of different types of cheese. For example, over fifty aroma-

active compounds have been detected in various cheddar

cheeses.

Thermal extraction (dynamic headspace) offers an

automated and versatile alternative to multi-step liquid

extraction and vacuum distillation. Cubed or grated cheese

mixed with distilled water can be incubated (e.g. using the

Markes µ-CTE) and purged with inert gas or pure air with

the vapours collected using on- or offline sorbent traps.

Subsequent analysis by TD-GC/MS or TD-GC with

olfactometry provides the full flavour and fragrance profile

of a sample.


Sampling: 2 g grated cheese mixed with 5 mL distilled water

and incubated in the µ-CTE at 30ºC. Vapours swept onto

Tenax TA tubes in a 70 mL/min flow of helium for 10 mins






Analysis: GC/MS Aroma/flavour profiling of cheese using the µ-CTE at 30ºC

n-C

8

He

xan

al

He

pta

no

ne

n-C

9

He

pta

na

l

He

xan

oic

acid

Pe

nta

me

thyl

he

pta

ne

Octa

na

l

Lim

on

en

e

No

na

na

l

De

ca

na

l

2-n

on

an

on

e


31

Background:

Burning mosquito coils indoors generates smoke that repel

mosquitoes. However, the smoke may contain pollutants of

health concern. Mosquito coils sometimes contain BCME

(bis[cloromethyl]ether) which is highly carcinogenic. It is

illegal to sell mosquito coils that contain BCME in the United

States. Nevertheless, mosquito coils that contain BCME

have occasionally penetrated the US market in recent years.

Two mosquito coils were purchased & analysed for BCME.

Using the Micro-Chamber/Thermal Extractor & UNITY 2, a

‘fingerprint’ of the chemical compostion of mosquito coils

may be established (see opposite). No BCME was found in

either of the coils tested in this case.


Sampling: Sections of each of the mosquito coils (one red,

one black) were lit & inserted into individual micro-

chambers. Vapours were swept onto Tenax TA/UniCarb

tubes in a flow of 150 mL/min of helium for 3 mins


Cold trap: U-T6SUL-2S (Sulphur trap)



Analysis: GC/MS

1 Propene

2 Methanol

3 Chloromethane

4 Methyl chloride

5 Acetone

6 Propanol

7 Furan

8 Acetic acid methyl ester

9 2,3-Butanedione

10 2-Butanone

11 Hexene

12 3-Methyl furan

13 Hexane

14 2-Methyl furan

15 Methyl proprionate

16 Benzene

17 1-Hydroxy-2-propanone

18 2-Pentanone

19 Pentadione

20 2,5,-Dimethyl furan

21 1-Methyl pyrrole

22 Toluene

23 Hexanal

24 Furfural

25 Ethyl benzene

26 Xylene

27 Styrene

28 Methoxy benzene

29 Benzaldehyde

30 Benzonitrile

31 Phenol

32 Benzofuran

33 Decene

34 Limonene

35 Phenyl ester acetic acid

36 Butyl benzene

37 2-Methoxy phenol

38 Benzoic acid methyl ester

39 2-Methyl benzofuran

40 Tetramethyl benzene

41 Phenylmethyl ester acetic

acid

42 2-Methoxy-4-methyl phenol

43 Naphthalene

44 2-Ethyl-2-methoxy phenol

45 Tridecane

46 Dimethoxy phenol

47 Biphenyl

48 Tetradecane

49 Pentadecene

50 Pentadecane

51 Allethrin

Quality control of mosquito coil emissions

Analysis of two lit mosquito coils by thermal extraction followed by TD-GC/MS

Red mosquito coil

Black mosquito coil


32

Background:

The Markes µ-CTE is ideal for fragrance profiling of aqueous

solutions and emulsions such as shampoo. Six replicate, or

different shampoo, samples can be measured into

individual micro-chambers and incubated at low

temperatures (e.g. 30-40ºC) to simulate body/shower

temperatures. The fragrance components are purged onto

attached tubes packed with hydrophobic sorbents which

allow quantitative retention of the organic compounds of

interest while water is purged to vent.

The µ-CTE is compatible with the use of air or

nitrogen/helium gas to allow analysis of product fragrance

under oxygenating or inert conditions.


Sampling: 5 mL shampoo incubated in the µ-CTE at 30ºC.

Vapours swept onto Tenax TA tubes in a 70 mL/min flow of

helium for 5 mins






Analysis: GC/MS

Fragrance profile from shampoo obtained using the Micro-Chamber/Thermal

Extractor under inert conditions

Eth

yl a

ce

tate

Cyc

loh

exa

ne

Bu

tan

oic

acid

3-m

eth

ylb

uta

no

l a

ce

tate

D-lim

on

en

e

He

xen

al

ace

tate A

ce

tic a

cid

, p

he

nyl

me

thyl

este

r

2-(

1,1

-dim

eth

yle

thyl

)-cyc

loh

exa

no

l

2-p

he

no

xye

thyl

iso

bu

tyra

te

Fragrance profiling of toiletries using the

Micro-Chamber/Thermal Extractor



33

Background:

Fragrance plays a major part in market acceptance and

consumer satisfaction for products such as toiletries (e.g.

soap), air fresheners and domestic cleaning materials.

Markes’ TD instrumentation provides a versatile, labour-

saving and automated tool for sensitive GC/MS analysis of

the fragrance profile of consumer products. Advantages

include:

• Numerous sampling handling options

• Selective elimination of potential interferences such as

water and some solvents, thus simplifying fragrance

analysis.

• Options for continuous online analysis, e.g. to monitor

the fragrance profile as it changes over time


Sampling: ~200 mL headpace sampled onto Tenax TA tubes



Split flow: 30 mL/min during tube & trap desorption

Analysis: GC/MS

Headspace from sample of fabric conditioner selectively concentrated onto a

Tenax tube and analysed by TD-GC/MS

He

xen

e-1

-ol

a-p

ine

ne

D-lim

on

en

eTr

ipla

l

Lin

alo

ol

a-c

ed

ren

e

Th

ujo

pse

ne

Me

thyl

-b-io

no

ne

Profiling the fragrance of consumer products


Background:

Manufacturers of fabric conditioners are interested in

knowing what fragrance compounds remain on the fabric

after washing as this gives the fabric the characteristic and

desirable ‘freshly washed’ smell.

In the example opposite, direct desorption of a small

sample of washed fabric was compared with that of a

fragrance standard. Results illustrate that a significant

portion of the fragrance has remained on the fabric after

the washing process.


Sampling: Direct desorption of washed fabric in an empty

sample tube. Liquid standard injected onto a Tenax TA tube


Desorption: 70ºC for 5 mins (fabric) 280ºC for 5 mins

(Tenax tube)




Analysis: GC/MS

Note: This application can also be carried out using HS-TD

or the Micro-Chamber/Thermal Extractor

Fragrance analysis of conditioned fabric by direct

desorption

Fragrance standard

Fabric sample desorbed at 70ºC

Markes International LtdT: +44 (0)1443 230935 F: +44 (0)1443 231531E: [email protected] W: www.markes.com34


35

Background:

Most natural (e.g. floral) fragrances, and many of the

fragrance profiles of consumer products (e.g. air

fresheners), change with time & ambient conditions.

Markes’ continuous & semi-continuous online monitoring

vapour systems offer around-the-clock profiling of fragrance,

& odour allowing changes to be tracked as a function of

time & ambient conditions; e.g. temperature, humidity,

sunlight intensity, etc.

Online TD systems from Markes include single trap

configurations based on UNITY 2 & dual trap configurations

based on the TT24-7. Both are electrically (Peltier) cooled so

no liquid cryogen is required. The twin traps of the TT24-7

operate reciprocally to monitor the air/gas continually (i.e.

with no dead time)

Typical online monitoring conditions:

TD system options: TT24-7, series 2 UNITY-Air Server/CIA 8,

series 2 UNITY-Direct Inlet Accessory

Sampling: 10-50 mL/min for 20 mins

Trap: U-T2GPH-2S (General purpose

hydrophobic)


Analysis: GC/MS

Concentrations of vapour phase organic compounds

changing with time

Time (hours:mins)

03:1205:59

08:05

Near real-time monitoring of fragrance profiles as

they change over time

Dual traps of the TT24-7


36


Monitoring the vapour profiles of burning incense

(joss) sticks over timeBackground:

Incense sticks are composed of aromatic plant materials

and essential oils, which release fragrant smoke when

burned.

The objective of this application was to determine the

components of the vapour from a burning incense stick

using TD, and also to track any changes in the vapour

profile for the duration of burning and after the stick was

extinguished.

Markes MTS-32 is an ideal sampling device for such an

application as it can be programmed to take multiple air

samples onto individual sorbent tubes sequentially at

regular time intervals.


Sampling: MTS-32 with Tenax TA/Unicarb tubes



Trap: U-T6SUL-2S (sulphur trap)

Trap conditions: -10°C to 300°C for 5 mins

Split: 15:1

Analysis: GC/MS

1 Propene

2 2-Methyl-propene

3 Acetic acid

4 3-Methyl-pentane

5 1,3,5-Trifluoro-benzene

6 Benzene

7 Heptane

8 Hexamethyl-cyclotrisiloxane

9 Octamethyl-cyclotetrasiloxane

10 2-Ethyl-hexanol

11 2,2'-Azobis[2-methyl-propanenitrile],

12 Nonanal

13 Benzenecarboxylic acid

14 1,3-Bis(1-methylethenyl)-benzene

15 1,3-Diisocyanato-2-methyl benzene

16 4-Methyl-1,3-benzenediamine

17 1,3-Dihydro-5-methyl-2H-benzimidazol-2-one

18 4-Methyl-8-quinolinol

19 1-(1-Isocyanato-1-methylethyl)-3-(1-

methylethenyl)-benzene

20 1,3-Bis(1-isocyanato-1-methylethyl)-benzene

21 n-Butyl-benzenesulfonamide

22 2-Ethylhexyl salicylate

23 7-Hexadecene

24 n-Hexadecanoic acid

25 7-n-Pentadecylaminomethyl-6-hydroxy-5,8-

quinolinedione

26 1-Octadecene

27 4,4'-(1-Methylethylidene)bis-phenol

28 Triphenylphosphine oxide

29 4-Methoxybenzonaphthone

1 7

6

5

4

32

14

1312

1110

9

818

17

21

19

20

1615

22 26

2324

25

28

29

27


37

Breath from six non-

smokers

Breath from two

smokers

Background:

We are what we eat, & sometimes it can come back to

haunt us! Halitosis can also be caused by bacterial

infections of the mouth/throat, some disease states and

smoking.

Markes offers a range of specialist sampling accessories for

thermal desorption, including the Bio-VOC breath sampler.

The Bio-VOC collects breath from the mouth and bronchial

passages, or from the alveoli (depending on application), &

transfers it to sorbent tubes for subsequent analysis by TD-

GC/MS. Applications of the Bio-VOC include biological

monitoring of environmental/workplace exposure & aiding

disease diagnosis, in addition to breath odour.


Sampling: Breath exhaled into Bio-VOC sampler &

transferred to Tenax TA tube or Tenax TA/Carbograph 1TD

focusing trap





Analysis: TD-GC/MS or TD with process-MS (as shown here)

= Benzene

= Toluene

= Isoprene

Rapid TD-MS analysis of benzene and other hydrocarbons in the breath of

smokers and non smokers

Bio-VOC breath sampler

Halitosis – bad breath


38


The Markes International advantage

Markes is the world leader in analytical thermal desorption and has

pioneered important technical innovations such as SecureTD-Q

(quantitative sample re-collection for repeat analysis), TubeTAG

electronic labels for sorbent tubes and universal (multi-application)

heated valve technology.

Markes leadership in TD now extends to:

• The widest available product portfolio and application

range

• Product quality and reliability

• Excellence in technical and applications support

Trademarks

UNITY™, ULTRA™, Air Server™, CIA 8™, TD-100™, µ-CTE™, SafeLok™, DiffLok™, VOC-Mole™,

Bio-VOC™, TT24-7™, TC-20™, TD-100™, UniCarb™, TubeTAG™ & SecureTD-Q™ are trademarks of

Markes International Ltd, UK

ClearView™, and TargetView™, are trademarks of ALMSCO International (a division of Markes

International Ltd)

Tenax® is a registered trademark of Buchem B.V., Netherlands

Carbograph™ is a trademark of LARA s.r.l., Italy

Carbopack™ is a trademark of Supelco Inc., USA

Silcosteel® is a registered trademark of Restek Inc., USA

For more information on Markes comprehensive range of thermal

desorption instrumentation and sampling accessories request your free

copy of Markes TD Accessories & Consumables catalogue


Markes International Ltd

Gwaun Elai Medi Science Campus

Llantrisant

RCT

CF72 8XL

United Kingdom

T: +44 (0)1443 230935 F: +44 (0)1443 231531

E: [email protected] W: www.markes.com

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Documents

Thermal Desorption Apps for Foods