EPA 9079 SCREENING TEST METHOD FOR POLYCHLORINATED BIPHENYLS

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1、METHOD9079SCREENINGTESTMETHODFORPOLYCHLORINATEDBIPHENYLSINTRANSFORMEROIL1.0SCOPEANDAPPLICATION1.1Method9079maybeusedtoscreenhydrocarbonbasedelectricalinsulatingfluidsforpolychlorinatedbiphenyls(PCBs)atpresetlevelsof20,50,100,or500µg/g.Themethodisdesignedtoprovidescree

2、ningdataoutsideofalaboratoryenvironmentinunder10minutes,providingacolorimetricindicationthattheconcentrationofPCBsisaboveorbelowthefixedendpoint.Screeningproceduresmaysignificantlyreducethenumberofsamplesrequiringlaboratorytesting.1.2ChlorinesareremovedfromthePCBmolec

3、uleusinganorgano-sodiumreagent.Theresultingchlorideionsaremeasuredusingacolorimetricindicator.1.3Thismethodisrestrictedtousebyorunderthesupervisionoftrainedanalysts.Eachanalystmustdemonstratetheabilitytogenerateacceptableresultswiththismethod.2.0SUMMARYOFMETHOD2.1Asam

4、pleoftheoiltobetestedisreactedwithamixtureofmetallicsodiumcatalyzedwithnaphthaleneanddiglymeatambienttemperature.Thisprocessconvertsallorganichalogenstotheirrespectivesodiumhalides.Allhalidesinthetreatedmixture,includingthosepresentpriortothereaction,arethenextractedi

5、ntoanaqueousbuffer,apremeasuredamountofmercuricnitrateisadded,followedbyasolutionofdiphenylcarbazoneastheindicator.2.2Thecolorofthesolutionattheendofthetestindicateswhetherthesampleisaboveorbelowthepresetchlorinelevel.Ayellowendpointindicatesaconcentrationgreaterthant

6、hesetpointofthetestandablue-violetendpointindicatesaconcentrationlessthanthesetpointofthetest.2.3TheendpointatwhicheachofthetestkitsturnspositiveiscalibratedusingAroclor1242standards.Aroclor1242providesaconservativeendpointduetoitslowchlorinecontentrelativetotheotherA

7、roclorsusedinelectricalequipment.AlistofAroclorsusedinelectricalequipmentandthePCBconcentrationthatgivesapositiveindicationusingthe50µg/gtestkitisgiveninTable1.3.0INTERFERENCES3.1Waterpresentinthesampleatmorethan2%maycausealowreading.Waterpresentatthishighalevelresult

8、sinanobviouschangeinthesodiumreactionandtheusershouldstopthetest.3.2Highsulfurlevels(4%)willcauseahighbiaspossiblyresultingi