EPA Method 508A Screening for Polychlorinated Biphenyls by Perchlorination

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1、METHOD508ASCREENINGFORPOLYCHLORINATEDBIPHENYLSBYPERCHLORINATIONANDGASCHROMATOGRAPHYRevision1.0T.A.Bellar--Method508A,Revision1.0(1989)ENVIRONMENTALMONITORINGSYSTEMSLABORATORYOFFICEOFRESEARCHANDDEVELOPMENTU.S.ENVIRONMENTALPROTECTIONAGENCYCINCINNATI,OHIO45268508A-1METHOD508ASCREENINGFORPOLYCHLORINATE

2、DBIPHENYLSBYPERCHLORINATION/GASCHROMATOGRAPHY1.0SCOPEANDAPPLICATION1.1Thisproceduremaybeusedforscreeningfinisheddrinkingwater,rawsourcewater,ordrinkingwaterinanytreatmentstageforpolychlorinatedbiphenyls(PCBs).ThisprocedureisapplicabletosamplescontainingPCBsassinglecongenersorascomplexmixturessuchas

3、weathered,intact,ormixturesofcommercialAroclors.TheprocedureisincapableofidentifyingtheparentPCBsbecausetheoriginalPCBsarechemicallyconvertedtoacommonproduct,decachlorobiphenyl(DCB).TheprocedurehasonlybeenevaluatedusingAroclorsand2-chlorobiphenylasasourceofPCBs.1.2Thisprocedureisprimarilydesignedto

4、functionasapass/failtestforDCBat0.5µg/L.However,itwillaccuratelymeasureDCBfromthemethoddetectionlimit(MDL)to5.0µg/L.ItispronetofalsepositiveinterferencesandcanresultinacalculatedweightofPCBssignificantlygreaterthanthatofPCBoriginallypresentinthesample.IfDCBisdetectedat0.5µg/Lorabove,thenanapprovedm

5、ethodfortheanalysisofPCBsshouldbeusedtoaccuratelyidentifythesourceandmeasuretheconcentrationofthePCBs.1.3ThisprocedurecanbeusedtohelpconfirmthepresenceofPCBsforothermethodsusingelectroncaptureorhalogenspecificdetectorswheneverchromatographicpatternsarenotrepresentativeofthosedescribedinthemethod.2.

6、0SUMMARYOFPROCEDURE2.1A1Lwatersampleisplacedintoaseparatoryfunnelandextractedwithmethylenechlorideoroneofseveraloptionalsolvents.Theextractisdried,concentrated,andthesolventisexchangedtochloroform.ThePCBsarethenreactedwithantimonypentachloride(SbCl)(inthepresenceofanironcatalyst5andheat)toformDCB.T

7、heDCBisextractedwithhexanefromthereactionmixture;aftertheextractispurified,analiquotisinjectedintoagaschromatograph(GC)equippedwithanelectroncapturedetector(ECD)forseparationandmeasurement.TheGCiscalibrated