METHYLENE CHLORIDEanalysis.docx
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METHYLENE CHLORIDEanalysis.docx
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METHYLENECHLORIDEanalysis
METHYLENECHLORIDE
Methodno.:
80
Matrix:
Air
Targetconcentrations:
500ppm(1736mg/m3)OSHAPEL
10ppm(34.7mg/m3)
Procedure:
SamplesarecollectedbydrawingairthroughglasssamplingtubescontainingCarbosieveS-III(carbonbasedmolecularsieve)adsorbent.Samplesaredesorbedwithamixtureof99:
1(v/v)carbondisulfide(CS2)/dimethyl-formamide(DMF)inthepresenceofanhydroussodiumsulfateandareanalyzedbyGCusingaflameionizationdetector.
Recommendedairvolume
andsamplingrate:
3Lat0.05L/min
Reliablequantitationlimit:
0.201ppm(0.697mg/m3)
Standarderrorsofestimate
atthetargetconcentration:
(Section4.7.)
5.8%(10ppm)
6.5%(500ppm)
Statusofmethod:
Evaluatedmethod.ThismethodhasbeensubjectedtotheestablishedevaluationproceduresoftheOrganicMethodsEvaluationBranch.
Date:
February1990
Chemist:
DonaldBurright
OrganicMethodsEvaluationBranch
OSHAAnalyticalLaboratory
SaltLakeCity,Utah
1.GeneralDiscussion
1.1.Background
1.1.1.History
Thisprocedureallowstheuseofasinglestandardsize(6-mmo.d.?
4-mmi.d.?
7cm)adsorbenttubeforthecollectionofmethylenechloride.Becausemethylenechloridereadilymigratesoncharcoal,earliermethodsrequiredtheuseoftwostandardsizecharcoaltubesconnectedinseries,whichcouldbeisolatedfromeachotheraftersampling,(Ref.5.1.)ortheuseofacustomdesignedjumbosizeadsorbenttubecontaininganinconvenientlylargeamountofcharcoal(Ref.5.2.).Thesetwoproceduresovercometheeffectsofmigrationbyeitherisolatingthebackupsectionfromthesamplingsectionsothatitwouldnotbecontaminatedbythemigratingmethylenechlorideorbyusingsuchalargequantityofcharcoalthatmigrationisslowedtoanacceptablerate.Thebenefitofasinglestandardsizeadsorbenttubeismadepossiblebytheuseofanadsorbentmaterial,CarbosieveS-III,whichdemonstratesnegligiblemethylenechloridemigration.CarbosieveS-III,availablethroughSupelco,Inc.,isasphericalcarbonmolecularsieveandhasasurfaceareaofabout800m2/g,aboutthesameascharcoal.
ThisevaluationwasperformedattwotargetconcentrationsbecausethecurrentOSHAPELformethylenechlorideis500ppm(TC-500)andOSHAisnowintheprocessof6(b)rule-makingtoreducetheoccupationalexposuretomethylenechloride.Forthepurposeofthisevaluation,10ppmwasselectedasthelowertargetconcentration(TC-10).AgoalofthisevaluationwastodevelopasamplingprocedurethatwillaccommodateboththecurrentPELandanewlowerlimitifoneispromulgated.ThecurrentACGIHTLVis50ppmandthecurrentNIOSHRELstatesthatexposuretomethylenechloridebecontrolledtothelowestfeasiblelevel.(Refs.5.3.-5.5.)
1.1.2.Toxiceffects(ThissectionisforinformationonlyandshouldnotbetakenasthebasisofOSHApolicy.)
Methylenechloridecanaffectthebodyifitisinhaled,swallowedorcomesincontactwiththeeyesorskin.Methylenechlorideisananestheticandinhalingthevapormaycausementalconfusion,light-headedness,nausea,vomiting,andheadache.Continuedexposuremaycauseincreasedlight-headedness,staggering,unconsciousness,anddeath.Highvaporconcentrationsmaycauseirritationoftheeyesandrespiratorytract.Exposuretotheliquidmaycauseirritationtotheskinandeyes.Extendedexposuretotheliquidbytheskinmaycauseskinburns.(Ref.5.6.)
Carbonmonoxideisametaboliteofmethylenechlorideinanimalsandhumans.NIOSHhasrecommendedthatifthecarbonmonoxideconcentrationisabove9ppm,eithertheconcentrationofmethylenechlorideorcarbonmonoxideshouldbereduced.(Ref.5.5.)
Onthebasisofcarcinogenicandtumorigenicresponsesinratsandmice,NIOSHrecommendsthatmethylenechlorideberegardedasapotentialoccupationalcarcinogen.(Ref.5.3.)
1.1.3.Workplaceexposure
Methylenechlorideisusedmainlyasasolventinpaintremovers,aerosolmixtures,chemicalreactionprocessesandasablowingagentforflexiblefoams.Photography,metal-work,refrigeration,chemicalprocessing,pharmaceutical,flexiblefoam,andfoodindustriesusemethylenechloride.(Ref.5.8.)Methylenechloridehasbeenusedtoextractheat-sensitivenaturallyoccurringsubstances,suchascocoa,ediblefats,spices,andbeerhops.Ithasalsobeenusedinthedecaffeinationofcoffee.(Ref.5.7.)
Approximately230millionkilogramsofmethylenechloridewereproducedintheUnitedStatesin1988.(Ref.5.9.)In1986,NIOSHestimatedthat1millionworkerswerepotentiallyexposedtomethylenechloride.(Ref.5.5.)
1.1.4.Physicalpropertiesandotherdescriptiveinformation(Ref.5.10.,unlessotherwisestated)
CASno.:
75-09-2
molecularweight:
84.93
molecularformula:
CH2Cl2
meltingpoint:
-97癈
boilingpoint:
39.8癈
vaporpressure:
53.3kPa(400mmHg)at24.1癈
vapordensity:
2.93(air=1)
specificgravity:
1.3266(water=1)
explosivelimit:
12%(lower)
19%(upper)(Ref.5.11.)
self-ignitiontemperature:
640癈(Ref.5.11.)
odor:
penetratingether-like
odorthreshold:
205-307ppm
appearance:
colorlessliquid
solubility:
1-2g/100mLofwater;solubleinmostcommonorganicliquids
synonyms:
dichloromethane;AerotheneMM;methylenedichloride;Narkotil;R30;Solaesthin;Solmethine;DCM;methanedichloride;methylenebichloride;NCI-C50102;UN1593(Ref.5.11.)
Theanalyteairconcentrationsthroughoutthismethodarebasedontherecommendedsamplingandanalyticalparameters.Airconcentrationslistedinppmarereferencedto25癈and101.3kPa(760mmHg).
1.2.Limitdefiningparameters
1.2.1.Detectionlimitoftheanalyticalprocedure
Thedetectionlimitoftheanalyticalprocedureis0.0746ngperinjection(1.0-µLinjectionwitha28:
1split).Thisistheamountofanalytethatwillgiveapeakwhoseheightisapproximately5timestheheightofthebaselinenoise.(Section4.1.)
1.2.2.Detectionlimitoftheoverallprocedure
Thedetectionlimitoftheoverallprocedureis2.09µgpersample(0.201ppmor0.697mg/m3).Thisistheamountofanalytespikedonthesamplingdevicethatallowsrecoveryofanamountofanalyteequivalenttothedetectionlimitoftheanalyticalprocedure.(Section4.2.)
1.2.3.Reliablequantitationlimit
Thereliablequantitationlimitis2.09µgpersample(0.201ppmor0.697mg/m3).Thisisthesmallestamountofanalytespikedonthesamplingdevicethatcanbequantitatedwithintherequirementsofarecoveryofatleast75%andaprecision(?
.96SD)of?
5%orbetter.(Section4.3.)
Thereliablequantitationlimitanddetectionlimitsreportedinthemethodarebaseduponoptimizationoftheinstrumentforthesmallestpossibleamountofanalyte.Whenthetargetconcentrationofanalyteisexceptionallyhigherthantheselimits,theymaynotbeattainableattheroutineoperatingparameters.
1.2.4.Instrumentresponsetotheanalyte
Theinstrumentresponseovertheconcentrationrangeof0.5to2timestheTC-10andTC-500targetconcentrationsislinear.(Section4.4.)
1.2.5.Recovery
Therecoveryofmethylenechloridefromsamplesusedin17-daystoragetestsremainedabove99.6%and97.3%attheTC-10andTC-500levels,respectively,whenthesampleswerestoredatabout22癈.Therecoveryofanalytefromthecollectionmediumduringstoragemustbe75%orgreater.(Section4.5.,regressionlinesofFigures4.5.1.1.and4.5.2.1.)
1.2.6.Precision(analyticalprocedureonly)
Thepooledcoefficientsofvariationobtainedfromreplicatedeterminationsofanalyticalstandardsat0.5,1and2timesthetargetconcentrationsare0.0330and0.0267attheTC-10andTC-500levelsrespectively.(Section4.6.)
1.2.7.Precision(overallprocedure)
Theprecisionsatthe95%confidencelevelforthe17-dayambienttemperaturestoragetestsare?
1.3%and?
2.7%attheTC-10andTC-500levelsrespectively.(Section4.7.)Theseeachincludeanadditional?
%forpumperror.Theoverallproceduremustprovideresultsatthetargetconcentrationthatare?
5%orbetteratthe95%confidencelevel.
1.2.8.Reproducibility
Sixsamples(TC-10)collectedfromacontrolledtestatmosphereandadraftcopyofthisprocedureweregiventoachemistunassociatedwiththisevaluation.Thesampleswereanalyzedafter11daysofrefrigeratedstorage.NoindividualsampleresultdeviatedfromitstheoreticalvaluebymorethantheprecisionreportedinSection1.2.7.(Section4.8.)
1.3.Advantages
BecausemethylenechloridedoesnotreadilymigrateonCarbosieveS-III,asinglestandardsizeCarbosieveS-IIIsamplingtubemaybeused.Thisisnotpermissiblewithactivatedcharcoalduetothemigrationofmethylenechloridefromthefrontsectiontothebacksection.
1.4.Disadvantages
1.4.1.ThefinemeshsizeofCarbosieveS-III(60/80)resultsinagreaterpressuredropacrossthesampletubethanoccurswiththeconventionalcoconutshellcharcoalsamplingtube.Thisresultsintheneedforthe0.05L/minsamplingrate.
1.4.2.Therecommendedsamplesizeis3Lasopposedtothe10Lsamplesizeofpreviousmethods.
2.SamplingProcedure
2.1.Apparatus
2.1.1.Samplesarecollectedusingapersonalsamplingpumpcalibratedtowithin?
%oftherecommendedflowratewiththesamplingdeviceattached.
2.1.2.Samplesarecollectedwith4-mmi.d.?
6-mmo.d.?
70mmglasssamplingtubespackedwithtwosectionsof60/80meshCarbosieveS-III.Thefrontsectioncontains130mgandthebacksectioncontains65mgofadsorbent.Thesectionsareheldinplacewithglasswoolplugs.Forthisevaluation,Supelco'sORBO-91CarbosieveS-IIItubes(catalogno.2-0360)wereused.
2.2.Reagents
Nosamplingreagentsarerequired.
2.3.Technique
2.3.1.Im
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