thermal desorption: a practical applications guide · thermal desorption: a practical applications...

32
Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing www.markes.com

Upload: hoangkhanh

Post on 07-Sep-2018

243 views

Category:

Documents


0 download

TRANSCRIPT

Page 1: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

Thermal Desorption:A Practical Applications Guide

II. Residual Volatiles & Materials Emissions Testing w

ww

.mark

es.co

m

Page 2: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

Introduction to MarkesInternational Ltd.

Formed in 1997, Markes International Ltd. is one ofthe world’s leading suppliers of thermal desorption(TD) equipment for monitoring trace toxic andodorous chemicals in air, gas and materials. Servingfast growing markets from environmental health andsafety to materials testing and from food / flavour /fragrance to defence / forensic, Markes’ globalcustomer base includes major industry, governmentagencies, academia and the service laboratory sector.

Markes has introduced several highly successfulbrands of TD instruments to the market including:UNITY™ – a universal TD platform for single tubes,the 100-tube ULTRA™ TD autosampler, theAir Server™ interface for canisters and on-linesampling, the µµ--CTE™ Micro-Chamber / ThermalExtractor for materials testing, the TT24-7™ forcontinuous on-line monitoring and the TC-20™ multi-tube conditioner.

Markes also supplies a wide range of samplingaccessories and consumables for all TD applicationareas.

What is TD?

Since the early 1980s, thermal desorption hasprovided the ultimate versatile sampleintroduction technology for GC / GC-MS. Itcombines selective concentration enhancementwith direct extraction into the carrier gas andefficient transfer / injection all in one fullyautomated and labour-saving package.

Markes International Ltd., UK headquarters

Page 3: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

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

Overview

Thermal desorption is now recognised as thetechnique of choice for environmental air monitoringand occupational health & safety. Relevant standardmethods include: ISO/EN 16017, EN 14662 (parts 1& 4), ASTM D6196, US EPA TO-17 and NIOSH 2549.Related applications include monitoring chemicalwarfare agents (CWA) in demilitarisation / destructionfacilities and civilian locations (counter-terrorism).

TD is also routinely used for monitoring volatile andsemi-volatile organic compounds (S)VOCs in productsand materials. Examples include residual solvents inpackaging & pharmaceuticals, materials emissionstesting and food / flavour / fragrance profiling.

This publication presents several real worldapplications of TD for measuring residual solventsand for materials emissions testing. Accompanyingpublications cover the application areas of:

• Food, flavour, fragrance & odour profiling

• Defence & forensic

• Environmental monitoring and occupationalhealth & safety

Residual Solvents & MaterialsEmissions Testing

TD provides a convenient and fully automatedalternative to conventional solvent extraction formeasuring residual volatiles. Products ranging fromointments to drug powders and from packaging filmsto polymer beads may all be weighed into emptysample tubes for direct desorption / extraction andtransfer of target analytes to the GC(-MS) analyser oreNose.

Vapour-phase organic chemicals are also emittedfrom a variety of construction products such aspaints, car trim components, carpets, moulded PVC,adhesives, etc. This causes elevated concentrations ofVOCs indoors and in vehicle-cabin air which mayhave adverse health effects.

Page 4: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

With the advent of new legislation requiring themeasurement and reporting of VOC emissions frommaterials there is increasing pressure onmanufacturers to test for the VOCs emitted from theirproducts. Standard methods for emissions testingspecify thermal desorption with GC-MS/FID andinclude: EN/ISO 16000(-6, -9, -10 & -11), ASTMD7143, ASTM D5116 and ASTM D6196.

Key Applications

Residual Volatiles:

• Pharmaceuticals / drug powders

• Ointments

• Packaging films

• Polymer beads

Emissions from Materials:

• Construction products e.g. paints

• Car trim components e.g. wood veneers,moulded PVC & adhesives

• Carpets and textiles

• Electronics

• Plastic toys

Direct DesorptionMaterials may be weighed into empty sample tubesfor direct thermal desorption / extraction of (S)VOCs.

Direct desorption is used for both:

• Complete (exhaustive) extraction, plus

• Characterisation of materials from arepresentative vapour profile

Direct TD provides information on VOC / semi-VOCcontent of materials which is complementary to thatobtained by conventional emissions testing. It alsofacilitates selective concentration of the compoundsof interest while water or other solvents are purgedto vent.

Compatible materials include: Solids (powders, fibres,films and granules), resins, pastes and liquids /emulsions.

Page 5: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

Direct desorption of packaging Background:VOCs in food packaging can cause taint. In thisexample, TD was used to analyse printed “energyfood bar” wrappers in two ways:• Direct desorption of the wrapper• Desorption of Tenax TA™ tubes used to collect

HS vapours from the sampleNote that direct TD (dynamic headspace) allowssimultaneous analysis of both volatiles and semi-volatiles whereas volatiles are preferentiallyconcentrated in the static HS sample.

Typical TD-GC conditions:Sample:10 x 5 cm area of film, rolled & insertedinto an empty glass tube for direct desorption &250 ml headspace sample drawn into a Tenaxsorbent tube TD system: ULTRA-UNITYDesorption: 10 mins at 60°C (direct TD) and 10mins at 300°C (HS sample on Tenax tube)

Trap: Quartz wool, Tenax TA, Carbopack X™

Split: 30:1Analysis: GC-MS Typical analytes:

Alcohols, esters, ketones, alkanes and other odoroussolvents

Direct desorption of “energy food bar” wrapper(insert) and headspace (HS) analysis of same

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

1-

Propan

ol Eth

yl a

ceta

te

Pentamethyl heptane

Penta

noic

aci

d 2

,2,4

-trim

ethyl

-3-

carb

oxyi

sopro

pyl

, is

obuty

l es

ter

Eth

yl a

ceta

te

Page 6: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

Direct desorption ofpharmaceutical powders

Background:Direct TD (dynamic headspace) analysis ofresidual volatiles in drugs eliminates manualsample preparation and offers >95% extractionefficiency thus simplifying calibration relative toconventional equilibrium headspace methods. Only2-10 mg of sample is required allowing themethod to be used for research compounds. Themethod is suitable for drugs in powder or granularform which melt before decomposition.

Typical TD-GC analytical conditions:Sample: ~3 mg powder (direct desorption)Desorption: 10 min at 225ºC Trap: Tenax

Split: To suit analyte concentration

Analysis: GC-FID or GC-MS

Reference: TDTS41 analysis of residualsolvent (dimethyl sulfoxide(DMSO)) in a drug precursor

~3 mg of development drug powder weighed into aPTFE tube liner & directly desorbed

Typical analytes:Solvents such as MEK, DMF, DMSO, etc.

Concentration: ppm to %

DM

SO

First Desorption

Second Desorption

Page 7: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

Direct desorption of ointment Background:Ointments present a very challenging matrix forGC requiring extensive sample preparation byconventional methods. Even after lengthy liquidextraction, steam distillation etc. residue from theointment base (e.g. petroleum jelly) can stillcontaminate the GC system and causeinterference. Direct desorption of a small sample of theointment smeared around the inner surface of aPTFE liner and inserted into a TD tube behind ashort bed of Tenax can overcome all these issues,allowing fast, automated and interference-freeanalysis with minimal sample preparation.

Analytical conditions will vary depending ontarget analytes but typically include:Gentle primary desorption (100 - 200ºC) for 5-10minsTenax or Quartz / Tenax focusing trap at +30ºCTypically double split 100 to 1000:1NB: Short beds of Tenax usually need replacingafter ~10 uses, but this will vary.

Reference: TDTS9 Monitoring materials andprocesses for trace level VOCs

Direct desorption of high molecular weightpolysiloxanes from white ointment

Typical analytes:Essential oils, menthol, camphor, polysiloxanes, etc.

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

Primary desorption

Blank 2nd desorption:No carryover

Page 8: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

Direct desorption of 3.3 mg of wet emulsion paint.Water selectively eliminated

Background:GC analysis of volatile organic content is sometimesused as an indicator of emission potential,particularly for liquid (wet-applied) constructionproducts such as paint (e.g. US EPA Method 311).However, conventional GC liquid injectors are proneto contamination during paint analysis – especiallyif the coating has a high solid content. Thermaldesorption completely overcomes this issue andoffers a labour-saving injection method forautomated GC analysis of paints and coatings.

Typical TD-GC analytical conditions:Samples are prepared by weighing or dispensing aknown volume of paint onto a glass wool plug in aPTFE liner. Subsequent direct TD at modesttemperatures (e.g. 200°C) allows completeextraction of volatiles and water while solids remainin the liner. Water is selectively eliminated from thefocusing trap (Tenax +30°C) allowing interference-free TD-GC analysis of target organics.

For other TD-GC conditions see “Paint flakes” below.

Reference: TDTS57 Characterisation of paintsamples by direct desorption TD-GC-MS

Wet paint - exhaustiveextraction for “content testing”

Typical analytes:Ketones & esters, glycolethers,texanol, aromatics

Concentration: ppm to %

Repeat desorption(No carry over)

Propyl

ene

gly

col

N-m

ethyl

pyr

rolid

one

Ben

zoic

aci

d

DO

W D

PnB

Texa

nol

Page 9: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

Direct desorption of dry paint flakes. Repeatdesorption shows complete extraction

Background:In accordance with indoor air qualityrequirements, paint manufacturers regularlymeasure VOC emissions from dried / curedproducts using standard emissions tests (seebelow). However, direct thermal desorption /extraction is also used as a quick, complementarycheck on the (S)VOC content of small samples ofdried paint flakes.

NB. Similar methodology can also be applied toforensic characterisation of paint.

Typical TD-GC analytical conditions:Sample mass: ~2 mgTD system: ULTRA-UNITYDesorption: 10 mins at 220°CTrap: Tenax at +30°CDouble split: 300:1Analysis: GC-MS (SCAN)

Reference: TDTS57 Characterisation of paintsamples by direct desorption TD-GC-MS

Paint flakes - exhaustiveextraction for “content testing”

Typical analytes:Ketones & esters, glycolethers, texanol, aromatics

Concentration: ppm to %

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

Original sample

Re-desorption

Nonylphenol isomers

Ben

zyl al

cohol

Xyl

enes

MBX

i-Buta

nol

Page 10: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

Textiles - leather discolouration Background:Troubleshooting problems affecting textiles andfurnishings can present an extremely challenginganalytical application by conventional extractionmethods. However, issues such as discolouration, off-odour, etc. can be readily evaluated by directlydesorbing a small section of the offending materialand comparing the VOC profile with that from acontrol portion. In this case TD was used to rapidlyidentify the cause of patchy yellow discolouration onwhite leather upholstery. The problem was found to behigh levels of residual natural oils in the yellowpatches.

Typical TD-GC conditions:Sample mass: ~30 mgTD system: ULTRA-UNITYDesorption: 5 mins at 150°CTrap: Quartz wool, Tenax TA, Carbograph 1TD™

Split: 14:1

Analysis: GC-MS (SCAN)

Reference: TDTS40 Direct desorption of volatileand semi-volatile organiccompounds from furnishingssuch as leather or textiles

Typical analytes:Nitrogenous compounds, substituted phenols,solvents & odorous / toxic organics e.g. sulphides,oxygenates etc.Concentrations: Low ppb to %

(S)VOC Profile for discoloured leather upholstery(top) and control portion (bottom)

SO

2

Die

thyl

ene

gly

col

1-M

ethyl

2-p

yrro

lidone

t-Buty

lphen

ol

Oct

yl-p

hen

ol is

om

er

Chlo

ro-t

riaz

ine

der

ivat

ive

Oct

yl-p

hen

ol is

om

er

Hep

tadec

anoic

aci

d

Fatt

y ac

ids

Nonan

al

Die

thyl

ene

gly

col

1-M

ethyl

2-p

yrro

lidone

2,2

-Buto

xyet

hoxy

ethan

ol

3 iso

mer

sTris-

chlo

ropro

pyl

phosp

hat

e

Palm

itic

aci

d

Ole

ic a

cid

Dio

ctyl

adip

ate

Yellowed leather -Note high oil

content

Control “white”leather showingdetergentresidue and lowoil levels

Det

ergen

t

Page 11: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

Direct desorption of vehicle trim Background:Emissions from vehicle trim components (PVC,polyurethane foam, adhesives, etc.) cansignificantly affect cabin air quality. The emissionlevel and potential impact of any given componentcan be evaluated by directly desorbing a smallsample of the offending material at lowtemperatures and determining the level of VOCsand SVOCs (fogging compounds) emitted underthese conditions.

Std Methods: VDA 278 and other company-specific protocols.

Typical TD-GC analytical conditions:Sample mass: ~30 mgTD system: ULTRA-UNITYDesorption: 30 mins at 90°C (VOC) 60 mins at 120°C (SVOC - fogging compounds)Trap: General purpose hydrophobic trap or TenaxAnalysis: GC-MS (SCAN)

Reference: TDTS59 Direct desorption of cartrim materials for VOC and SVOC analysis inaccordance with method VDA 278

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

Typical analytes:• Volatiles: Ethyl benzene, toluene, xylene,

styrene, acetaldehyde, tetradecane• Fogging: Di-n-butylphthalate, di-n-ethyl hexyl

phthalate

Concentrations: ppm to %

VOC (top) and SVOC (bottom) analyses fora PVC simulated leather car trim component

VOC

Foggingcompounds

Tolu

ene

Isopro

pyl

alc

ohol

1-M

ethoxy

-2-p

ropyl

acet

ate

2-E

thyl

hex

anol

2-E

thyl

1-h

exan

ol

1-M

ethyl

-2-p

yrro

lidin

one

2-(

2-B

uto

xyet

hoxy

)-et

han

ol

Buty

late

d h

ydro

xyto

luen

e2,6

-Di-

tert

-buty

l-4-s

ec-b

uty

lphen

ol

Dec

aned

ioic

aci

d,

dim

ethyl

est

er

2-H

exyl

-1-d

ecan

ol

Dec

anoic

aci

d d

ecyl

est

er

1,1

’-O

xybis

dec

ane

Buty

late

d h

ydro

xyto

luen

e

Ben

zam

ide

Di-

isodec

yl p

hth

alat

eD

idec

yl p

hth

alat

e

Bis

(2-e

thyl

hex

yl)

sebac

ate

Di-

n-d

ecyl

phth

alat

e

Page 12: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

Materials Emissions Testing

Method compliant emissions testing equipment (cellor chamber) is used for certification testing of VOCemissions from materials by accredited laboratoriesand research facilities. Markes new Micro-chamber/ Thermal Extractor (µ-CTE) complements thesesystems by providing manufacturing industry with apractical tool for rapid, in-house quality control of theVOC content or emissions of products.

Micro-chamber / Thermal Extractor(µ-CTE)

The µ-CTE comprises sixindividual micro-chambers(28 mm deep x 45 mmdiameter). These allowsurface or bulk emissionsto be tested from up to sixsamples simultaneously attemperatures fromambient to 120°C.

A controlled flow of pureair / inert gas (10-500ml/min) is passed through all chamberssimultaneously to sweep emitted vapours ontoattached sorbent tubes or DNPH cartridges. Nopumps are required.

FLEC® Cell

The Field and LaboratoryEmission Cell (FLEC) is aneasy-to-use device for thecertification of indoorproducts / materialsaccording to their VOCemissions (EN/ISO 16000-10, ASTM D7143).

It differs from conventional chambers because it isopen on one side. This open side is placed onto theplanar surface of the sample such that the materialssurface effectively becomes part of the emission cell.Sample holders are available for compressiblematerials.

Pure humidifed air enters around the perimeter of thecell and emitted vapours are pumped onto 1 or 2sorbent tubes attached to the FLEC exhaust.

Vapour Analysis

In either case (µ-CTE or FLEC), emitted VOCs areanalysed by TD-GCMS/FID (ISO 16000-6, ASTMD6196 etc.). Formaldehyde is analysed byderivitisation with DNPH followed by HPLC (ISO16000-3, ASTM D5197, etc.).

Page 13: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

Typical analytes:VOCs (ranging in volatility from n-C6 to n-C16), glycolethers, esters, aromatics. SVOCs (generally lessvolatile than n-C16).

Concentrations: ppm to % in paint & ppbto ppm in emissions

Paint - FLEC cell Background:The FLEC cell provides an easy-to-use device formonitoring emissions from the surface of planarmaterials such as wall coverings, paint, carpetsand other floor coverings.

Std Methods: ENV 13419-2, EN/ISO 16000-10,ASTM D7143-05

Typical FLEC TD-GC analytical conditions:Sample area: 177 cm2

Test time: Equilibration 24 hrs (certification tests),1-2 hrs (routine). Vapour sampling: 15-30 minsTD system: ULTRA-UNITYCold trap: Tenax TA

Analysis: GC-MS (SCAN)

References: TDTS70, 71 & 72 Using the FLECcell for emissions testing, TDTS 55 Materialsemissions testing using FLEC, TDTS 56 TD-GC-MS analysis of materials emissions

Data courtesy of BRE, UK.

FLEC-TD-GC-MS analysis of emissions from waterbased emulsion paint

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

Car

bitol

Texa

nol 1

Texa

nol 2

Page 14: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

Typical analytes:VOCs (ranging in volatility from n-C6 to n-C16), glycolethers, aldehydes, monoterpenes & fatty acids.SVOCs (generally less volatile than n-C16).

Concentrations: ppm to % in flooring &ppb to ppm in emissions

Rubber flooring - FLEC cell Background:FLEC is portable and may be used for non-destructive emissions testing of products alreadyinstalled in a building. Testing emissions fromresilient flooring is a common FLEC application. For field work and as a quick check on productionQC, FLEC may be used with only 1-2 hourequilibration.

Typical FLEC TD-GC analytical conditions:

Sample area: 177 cm2

Test time: Equilibration 24 hrs (certification tests),1-2 hrs (routine). Vapour sampling: 15-30 minsTD System: ULTRA-UNITYCold trap: Tenax TA

Analysis: GC-MS (SCAN)

References: TDTS70, 71 & 72 Using the FLECcell for emissions testing, TDTS 55 Materialsemissions testing using FLEC, TDTS 56 TD-GC-MS analysis of materials emissions

FLEC-TD-GC-MS analysis of emissions from rubberflooring

Data courtesy of Prof. Dr. Peder Wolkoff, DK

Penta

nal

Hex

anal

α-Pi

nen

e

2-B

uto

xy e

than

ol

3-C

aren

e

Oct

anal

Hex

anoic

aci

d

Nonan

al

Proprionic

aci

d

Page 15: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

Automating the analysis of trace toxics in emissions data

Background:Back-pressure regulated EPC control of carrier gasthrough the entire UNITY TD-GCMS systemstabilises retention times independent of sorbentselection, desorption temperatures, split flows etc.This subsequently allows automatic reprocessingusing commercial third party GC softwarepackages.

This example shows automatic implementation ofNIST “AMDIS” spectral deconvolution software,allowing trace target analytes to be quickly,reliably and automatically identified in a complexchromatogram.

Typical TD-GC analytical conditions:TD system: ULTRA-UNITYSampling: 1.3 L office air collected on Tenax tubeDesorption: 10 mins at 300°CSplit: Outlet only ~5:1Trap: Material Emissions cold trapAnalysis: GC-MS (SCAN) with non-polar capillarycolumn.

Reference: TDTS66 Enhanced analysis oftrace toxics in materials emissions data

Chromatogram of indoor air sample and associatedspectral deconvolution report. 31 compounds werepositively identified within 3 mins with RT +/- 5

seconds and >80% spectral match.

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

Page 16: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

Rapid material emissionstesting using the µ-CTE

Background:Many standard emissions testing methods specifytime consuming and prohibitively expensiveprocedures using conventional test chambers. TheMarkes Micro-Chamber / Thermal Extractor (µ-CTE) provides a rapid and low cost alternative,offering parallel, ambient temperature surfaceemissions testing of up to 6 samplessimultaneously in a small bench-top device. The µ-CTE is also capable of performing elevatedtemperature bulk emission / “thermal extraction”testing. It is ideal for routine QA / QC of materialsin production or for in-house evaluation ofcompetitive or prototype products.

Typical test conditions:µ-CTE gas flow: 10-500 ml/min (no pumps req’d)Temperature: Ambient to 120°CSample quantity: 1-6 simultaneouslyTest time: typically <30 minutes Vapour collection: Tenax tubes or DNPH cartridgesAnalysis: TD-GC-MS/FID or HPLC (forformaldehyde derivative)

Reference: TDTS67 Micro-Chamber / ThermalExtractor (µ-CTE)

Chromatogram of emissions from a vinyl floor tile

Spacers

Sample

Unique flow control device

Heated airsupply

Heated chamber lid

Sample tube

Micro-chamber

Schematic of asingle micro-chamber

Propyl

ene

gly

col

α-Pi

nen

e

1-H

exan

ol, 2

-eth

yl

Ace

tic

acid

, 2-e

thyl

hex

yl e

ster

Buty

late

d h

ydro

xy t

olu

ene

N-H

exad

ecan

oic

aci

d

Page 17: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

Alkane recovery from u-CTE compared to a spiked sorbent tube

0

20

40

60

80

100

120

n-no

nane

( C9)

n-de

cane

(C10

)

n-un

deca

ne (C

11)

n-do

deca

ne (C

12)

n-tet

rade

cane

(C14

)

n-pe

ntadec

ane (C

15)

n-he

xade

cane

(C16

)

n-he

ptadec

ane (C

17)

n-oc

tade

cane

(C18)

n-eic

osan

e (C20

)

n-tet

raco

sane

(C24

)

n-Alkane

No

rmal

ised

pea

k ar

eas

Spiked Tube

Collected from u-CTE

Quantitative SVOC analysisusing the µ-CTE

Background:Vapour phase semi-volatile emissions are prone tocondensation and present a challenge toquantitative analysis. Independent heating of theinert µ-CTE pots, lids and gas lines ensuresquantitative recovery of SVOCs through the µ-CTE and onto the attached Tenax tube. This isdemonstrated by comparing TD-GC-MSchromatograms from an alkane test mix (C9-C24)spiked onto a sorbent tube and the same volumeof the alkane test mix extracted from a micro-chamber. Excellent recovery from the µ-CTE wasobserved for the entire volatility range of the testmix (see opposite).

µ-CTE Conditions:Gas flow: 50 ml/min (no pumps required)Temperature: 120°CTest time: 10 minutes Sample quantity: 1 µl of C9 - C24 test mix

Sorbent tube: Tenax TADesorption: 10 mins at 300°CSplit: ~30:1Analysis: GC-MS

Data for 1 µl solutions of semi-volatile alkanes(C9 – C24 ) thermally extracted from a sorbent tube

(blue bars) and a Micro-Chamber / Thermal Extractor(purple bars).

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

Page 18: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

Correlation between the µ-CTE& conventional emissions test

chambers

Background:Conventional material emissions chambers (EC)range in volume from ~20 L to 1 (or 5) m3 Theconditions within the chamber are controlled tosimulate real use conditions (~23 to 28°C / 50%relative humidity). The µ-CTE provides a costeffective alternative for surface emissions testingand correlates well with conventional chambermethods.

Agreement between the µ-CTE and a 1 m3

chamber after 72 sample hours equilibration isshown opposite.

Comparison of EC & µ-CTE parameters:

Area specific emission rates determined for the µ-CTE(up to 72 hours) and an emission chamber (72 hours)

for a building product. Excellent agreement isobserved between the two methods at 72 hours.

Area Specific Emission RatesCalculated for a 1 m3 EmissionChamber (red) and µ-CTE (blue)up to 3 days

0 days 1 day 3 days

Parameter µ-CTE EC

Sample area (m2) 1.282 x 10-3 1

Chamber volume (m3) 3.2 x 10-6 1

Load Factor (m2/m3) 400 1

Exchange rate (h-1) 1875 1

Gas Supply (L/min) 0.1 16.7

Chamber Temp. (°C) 23 23

Reproduced with kind permission fromFraunhofer Wilhelm-Klauditz Institute, Germany

Page 19: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

Multi-sorbent cold trap for simultaneous VOC & SVOC

analysis

Background:Markes has developed a special multi-sorbentfocusing trap for simultaneous measurement ofVOC and SVOC emissions. Vapours enter the trapthrough weak sorbents at the inlet / outlet endwhere semi-volatiles are retained. Volatiles aretrapped by the stronger sorbents at the rear of thetrap. During secondary (trap) desorption, carriergas flows are reversed to 'backflush' volatile andsemi-volatile analytes from the trap simultaneously.High boiling compounds never come into contactwith the stronger sorbents at the back of the trapand are quantitatively recovered (see n-C6 to n-C40analysis opposite). This increases samplethroughput and allows all materials emissionsapplications to be carried out using a single Markes(ULTRA-)UNITY TD configuration.

Analytical conditions:Standard loaded onto Quartz / Tenax tubesDesorption: 10 mins at 320ºCMaterial emissions cold trap -10 to +320ºCOutlet split only: 20:1Analysis: GC-MS (SCAN)

Reference: TDTS64 Simultaneous VOC andSVOC analysis

Multi-sorbent cold trap (top) and C6 to C40 in oneanalysis (bottom)

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

Gas flow during focusing

Gas flow during trap desorption

Very weak Weak Medium

C6

C14

C12

C11

C10

C9

C8C

7 C15

C16

C24

C18

C17

C20

C28

C32

C38

C40

UNITYfocusing

trap

Page 20: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

Construction products -adhesives

Background:Indoor air contaminants emitted by someadhesives and sealants are odorous and potentialthroat and airway irritants. Manufacturers aredeveloping water-based, low-emission products tominimise emission levels.Markes 100-tube ULTRA-UNITY TD system is usedwith Tenax tubes and GC-MS/FID for formaltesting of emissions from adhesives usingconventional small test chambers as per methodEN 13999 (shown opposite). The µ-CTE could alsobe used with ULTRA-UNITY-GC-MS/FID for rapidscreening of new adhesives under development, ifrequired.

Standard method: EN 13999

Typical TD-GC conditions:Sorbent tube: Tenax TD system: ULTRA-UNITYPrimary desorption: 10 mins at 280ºCTrap: U-T11GPC general purposeSplit: 5:1 on outlet onlyAnalysis: GC-MS/FID

TD-GC-MS/FID of adhesive sample

Typical analytes:Ketones, glycol ethers, solvents, hydrocarbons,aromatics, plasticizers

Concentration: ppm - % (Varies dependingon adhesive type)New, very low-emission adhesives (as shown) release~500 µg/m3 (~0.1 ppm) after 10 days.

Ace

tone

Reproduced with kind permission from Dr Decio, Dr Leoniand colleagues at MAPEI S.p.A., Milan, Italy

Ace

tic

acid

TH

F

1,2

-Eth

ane

dio

l

Tolu

ene

n-D

ecan

e

Inden

e Nap

hth

alen

e

BH

T

FID

MS

Page 21: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

Emissions from moulds usingthermal desorption

Background:Some VOCs are emitted as metabolic bi-productsof microbial or mould / fungal growth and havebeen termed microbial volatile organic compounds(MVOCs)1-3.

Methyl benzoate has been reported as a metabolicbiomarker for mould, and is used to detect andassess the extent of mould growth on dampsamples4.

The amount of methyl benzoate present inbuilding materials can be determined either by:

(a) Placing a sample of the test material intothe µ-CTE and collecting the emittedMVOCs onto Tenax tubes at near ambienttemperatures, or

(b) Sampling the indoor air using pumpedTenax tubes followed by subsequent TD-GC-MS analysis to identify methylbenzoate or other MVOCs.

TD-GC-MS of methyl benzoate “marker”

Met

hyl

ben

zoat

e

References:1. Health Implications of Fungi in Indoor

Environments, Elsevier / North-Holland Biomedical Press, Amsterdam (1994), 46–52

2. Int. Biodeterior. Biodegrad. (1989), 259–2843. Int. Biodeterior. Biodegrad. (1991), 487–4894. J. Sep. Sci. (2005), 28, 2517–2525)

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

Page 22: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

VOC & formaldehydeemissions from vehicle interior

trim using µ-CTE

Background:The potential effect of a given vehicle interior trimcomponent on car cabin air quality can beassessed by materials emissions testing using a1m3 chamber at elevated temperatures (65°C)(VDA Method 276). The µ-CTE can also be usedfor testing emssions from car trim components;either at ambient temperature (as shown) or at65°C for correlation with VDA 276. The µ-CTEallows up to 6 different materials to be evaluatedevery few minutes with sample collection on eitherDNPH cartridges (formaldehyde) or sorbent tubes((S)VOCs).

Standard methods: VDA 276 & other companyspecific protocols.

µ-CTE Conditions:Trim material: Polyurethane foam

VOCs Sampled: 20°C for 10 mins at 100 ml/minonto Tenax tubes.Analysis: TD-GC-MS

Formaldehyde sampled: 20°C for 120 mins at 120 ml/min onto DNPH cartridges.Analysis: HPLC / UV detection

Emissions from polyurethane foam car trimcomponent. Formaldehyde / HPLC chromatogram(top) & VOC / TD GC-MS chromatogram (bottom)

Reproduced with kind permission from the InternationalAutomotive Research Centre, UK.

Typical analytes:Aldehyes, ketones, free fatty acids, esters, aromatics

Concentration: ppm to % (materials) & ppbto ppm (emissions)

Tolu

ene

Man

gan

ese(

II)

acet

ate

Bic

yclo

[4,2

,0]

oct

a-1,3

,5-t

rien

e

Buty

late

dhyd

roxy

tolu

ene

Ace

tone

Ace

tald

ehyd

e

Form

aldeh

yde

Propio

nal

deh

yde

MEK

Butr

ylal

deh

yde

Hex

anal

deh

yde

Page 23: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

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

Emissions from timber andwood-based products

Background:Timber and wood-based products are usedextensively for building construction, interiordesign and furniture manufacture. The wood andwood-products industries have always taken a leadin emissions testing, producing their ownstandards for formaldehyde emissions testing (e.g.EN 717) and actively participating in thedevelopment of methods for other VOCs – forexample EN/ISO 16000-6, -9, -10 and -11.In this example, Markes µ-CTE was used to testemissions from wood veneers used in cars.Samples were tested at ambient temperatureusing sorbent tubes to collect emitted VOCs(subsequent analysis by TD-GC-MS/FID) andDNPH cartridges to measure formaldehyde andother carbonyls (subsequent analysis by HPLC).

µ-CTE Conditions:As above

Reproduced with kind permissionfrom the International AutomotiveResearch Centre, UK.

Emissions from wood veneer. Formaldehyde / HPLCchromatogram (top) & VOC / TD GC-MS

chromatogram (bottom)

Typical analytes:Aldehyes, ketones, free fatty acids, esters and aromatics

Concentration: ppm to % (materials) & ppb to ppm (emissions)

Form

aldeh

yde

Ace

tald

ehyd

e

Ace

tone

Acr

ole

in

Propio

nal

deh

yde

Cro

tonal

deh

yde

MEK

Butr

ylal

deh

yde

Ben

zald

ehyd

e

Val

eral

deh

yde

2-B

uta

none

Eth

yl a

ceta

te

Ace

tic

acid

, buty

l es

ter

1-M

ethoxy

-2-p

ropyl

ace

tate

1,3

,-D

imet

hyl

ben

zene

Sty

rene

Xyl

ene

Propen

oic

aci

d,

2 e

thyl

hex

yl e

ster

Trim

ethyl

-1,3

-pen

taned

iol

diis

obuty

rate

1,2

-Ben

zened

icar

boxy

lic a

cid,

bis

(2-m

ethyl

pro

pyl

) es

ter

Page 24: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

Emissions from textiles Background:Emissions from textiles, particularly childrensclothing, is gaining prominence in Europe, wherelegislation is dictating that more and moreproducts are certified with respect to their VOCemissions levels.Chemicals emitted from a 100 mm x 50 mmsection of nylon were collected onto a Tenaxsorbent tube using the µ-CTE. Key compounds ofinterest in this case are phenol and 2-phenoxyethanol. Phenol is used in the production ofcaprolactam which is an intermediate in themanufacture of nylon1. The resulting TD-GC MSanalysis, opposite, also shows high levels ofresidual 2-phenoxy ethanol, a solvent used intextile dyeing, being emitted from the fabric.

µ-CTE conditions:Temp: 40 ºCFlow: 100 ml/minSampling time: 10 min onto Tenax tubes

1. Agency for Toxic Substances and Disease Registry(ATSDR). Toxicological Profile for Phenol. U.S. PublicHealth Service, U.S. Department of Health and HumanServices, Atlanta, GA. (1989)

Low temperature emissions from nylon sampled usingthe µ-CTE and analysed using TD-GC-MS

Concentrations: ppm levels in textiles, ppbto ppm levels in vapour emissions

12

3 45

6

7

1. Hexanal2. Phenol3. Nonanal4. 2-Ethyl hexanoic acid5. Decanal6. 2-Phenoxy ethanol7. Cyclotetracosane

Page 25: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

Emissions from childrens’plastic toys using the µ-CTE

Background:VOCs from toys were thermally extracted andidentified in accordance with method prEN 71-11:2003. A typical chromatogram for plasticanimal figurines is depicted opposite. Compoundsranging in volatility from C7 - C24 were identified.

Note that the micro chambers of a Markes µ-CTEthermal extractor system have sufficient capacityto allow vapour-phase emissions to be tested fromwhole toys or large sections of toys.

Standard Method: prEN 71-11:2003

µ-CTE Conditions:Gas flow: 100 ml/minTemperature: 40°CSorbent tube: TenaxTest time: 15 minsAnalysis: TD-GC-MS

Thermal extraction of VOC from childrens’ plastic toys

Analytes:1. Toluene 6. 2-Butoxy ethanol2. Ethyl benzene 7. Tricyclodecane3. p-Xylene 8. Diethyl phthalate4. o-Xylene 9. Dibutyl phthalate5. Cyclohexanone 10. Dioctyl phthalate

1

2

3

45

6

7 10

98

Plastic toy placed in micro-chamber

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

Page 26: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

Semiconductor - labile andhigh boiling compounds

Background:The presence of volatile and semi-volatile organicvapours can adversely affect the growth of siliconwafer crystals and the resultant performance ofmicroprocessors, data storage devices and otherkey electronic components. The atmosphericconcentration of these contaminants in clean roomfabrication facilities is thus a critical issue. Thepurity of clean room atmospheres must becontrolled with respect to both particulates andvapours.

Typical TD-GC analytical conditions:Sampling: Pumped sampling onto Silcosteel™ orglass tubes packed with Quartz / Tenax or carbonblack sorbents

Desorption: 10 min at 320ºC (Tenax) or 12 min at360ºC (carbon black)

Trap: U-T1HBL or UNITY “DHS” application trap

Split: Typically 10:1 or less

Analysis: GC-MS

Reference: TDTS14, TDTS53 & TDTS 62concerning materials emissions of highboiling species in the semiconductor industry

A semiconductor manufacturer clean-roomenvironment and chromatogram of clean-room air

Analytes:Palmitic acid, butylated hydroxytoluene, triphenylphosphate, oxybenzone, caprolactam, diethylhexylphthalate, DC704 (phenyl silicone)

Concentration: Sub to low-ppb

Page 27: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

Semiconductor - outgassingfrom computer components e.g.

data storage devices

Background:The performance of data storage devices such ashard disk drives (HDD) can be adversely affectedby sources of Airborne Molecular Contamination(AMC) such as (i) outgassing from clean roomconstruction products, and (ii) emissions from PCcomponents e.g. HDD. It is, therefore, crucial fordisk drive manufacturers to minimise emissionsfrom component parts.

Typical TD-GC analytical conditions:Sampling device: Samples are placed in emissionchambers or the µ-CTE and off-gassed at elevatedtemperature (typically ~85ºC)

Sorbent: Vapours collected on DHS sorbent tubes

Desorption: 10 min at 320ºC

Trap: U-T1HBL or UNITY “DHS” cold trap

Split: 15:1

Analysis by GC-FID or GC-MS

Reference: TDTS14, TDTS53 & TDTS 62concerning materials emissions of highboiling species in the semiconductor industry

(S)VOC emissions from PC motor incubated at 85°Ccollected onto a tube packed with two carbon black

sorbents

Typical analytes:• Sticky high molecular weight (e.g. phthalates)• Chemically aggressive (e.g. organic sulphur species)

• Adhesive compounds (e.g. acrylates)

Concentration: Typically ppb levelemissions

Tolu

ene

Eth

yl h

exan

al

Eth

yl h

exan

ol

Dip

hen

ylm

ethan

e

Ben

zoic

aci

dphen

yl e

ster

SecureTD-QTM re-collection andrepeat analysis shows completerecovery of all analytes.

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

Page 28: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

TD-GC-MS analysisof vapourscollected duringTGA tests ofpolystyrene showover 30components overand above styreneand styrene dimer.These are due tochemicaldecomposition ofadditives such asanti-oxidants andprocess enhancers

Characterising evolved gasesduring TGA analysis

Background:Thermogravimetric Analysis (TGA) measures changesin the mass of a sample as it is heated. TGA is moreversatile than pyrolysis because it may be carried outunder either inert or oxidative atmospheres. Thetechnique is used extensively to characterise polymericand pharmaceutical materials (man-made fibres /textiles, polymeric films, paints, bulk plastics, etc).

Markes sorbent tubes may be coupled to TGAequipment to collect gases evolved as the sample isheated. In the example opposite, TD-GC-MS analysisof gases evolved during TGA of polystyrene provided adetailed profile of chemical decomposition productsand aided interpretation of the TGA data.

Typical analytical conditions:As below

Reference: Lever, T. J.; Price, D. M.; Warrington, S. B.; Evolved Gas Collection froma Thermogravimetric Analyzer andIdentification by Gas Chromatography-MassSpectrometry. Proc. 28th North AmericanThermal Analysis Society Conference, October4-6 (2000) Orlando, Florida, USA, pp. 720-725

Thermo-gravimetricanalysis ofpolystyrene withand withoutevolved gascollection, showsthat vapourcollection hasnegligible impacton the TGA data

Sty

rene

Styrenedimer

Page 29: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

Characterising materials viaTGA evolved gas analysis

Background:TGA coupled with TD-GC-MS analysis of evolvedgases can be used to identify unknown materials.In this example; Nylon 4,6 was identified from itstwo-step TGA profile and ratio of 2-pyrrolidoneand caprolactam in the total ion chromatogram ofevolved gases.

Note that two or more separate evolved gassamples can be collected from a single sample ifrequired – corresponding to different temperatureranges or weight loss steps in the TGA profile. Thisallows independent chemical analysis of theprocesses occurring at each stage of the thermo-gravimetric analysis.

Typical analytical conditionsTGA: 10ºC/min, ambient to 600ºC, N2 purge

Tube: Tenax with Carbograph 1TDDesorption: 3 mins at 50ºC & 5 mins at 250ºCCold trap: U-T2GPH or U-T11GPC (2-bedhydrophobic) -10 to 300ºCDouble split at ~500:1Analysis: GC-MS(SCAN)

TGA tests on an unknown sample of nylon (bottom).TD-GC-MS analysis of vapours collected during TGA

tests confirm Nylon 4,6 (Top).

2-p

yrro

lidone

Cap

rola

ctam

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

Page 30: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

Permeation testing using the µ-CTE

Background:Permeability is tested, typically at ambient or nearambient temperatures, using a special, proprietary1

permeation accessory for the Markes µ-CTE device.

A small droplet of test compound is first placed in awell at the bottom of the permeation accessory.Then a sample of the test material is stretchedover the top and sealed around the perimeter asshown in the top photograph opposite. The testmaterial does not come into direct contact with thetest compound. The complete assembly is thenplaced inside one of the µ-CTE micro-chambers.The µ-CTE has capacity for up to 6 samplematerials or test compounds to be testedsimultaneously. Clean air is passed over thesurface of the stretched material in each micro-chamber. Permeation of the test compound throughthe stretched material is assessed by monitoringthe air exhausting from the micro-chambers usingsorbent tubes and TD-GC-MS analysis in thenormal way.

Key applications include tests on protectiveclothing such as rubber gloves

µ-CTE permeationaccessory with testmaterial installed

1. UK patent application 0501928.6

Permeation accessoryplaced into one of 6micro-chambers inthe µ-CTE

Page 31: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

The Markes International advantage

• Markes leads the market in TD

• Unparalleled reputation for product quality andreliability

• Excellence in technical and applications support

• For further information on Markescomprehensive range of instruments, samplingaccessories and consumables please use one ofthe contact numbers / email address below orbrowse the web site

Trademarks

UNITY™, ULTRA™, Air Server™, µ-CTE™, TT24-7™, TC-20™, and SecureTD-Q™are trademarks of Markes International Ltd., UK

Tenax TA™ is a trademark of Buchem B.V., Netherlands

Carbograph 1TD™ is a trademark of LARA s.r.l., Italy

Silcosteel™ is a trademark of Restek Inc., USA

Carbopack X™ is a trademark of Supelco Inc., USA

FLEC® is a registered trademark of Chematec, Denmark

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

The Markes International team

Page 32: Thermal Desorption: A Practical Applications Guide · Thermal Desorption: A Practical Applications Guide II. Residual Volatiles & Materials Emissions Testing . ... safety to materials

ww

w.m

ark

es.co

m

Markes International Ltd.

Gwaun Elai Medi Science CampusLlantrisant

RCTCF72 8XL

United Kingdom

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