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1、METHOD8265VOLATILEORGANICCOMPOUNDSINWATER,SOIL,SOILGAS,ANDAIRBYDIRECTSAMPLINGIONTRAPMASSSPECTROMETRY(DSITMS)1.0SCOPEANDAPPLICATION1.1Thismethodusesdirectsamplingiontrapmassspectrometry(DSITMS)fortherapidquantitativemeasurement,continuousreal-timemonito
2、ring,andqualitativeandquantitativepreliminaryscreeningofvolatileorganiccompounds(VOCs)inwater,soil,soilgas,andair.DSITMSintroducessamplematerialsdirectlyintoaniontrapmassspectrometerbymeansofasimpleinterface(suchasacapillaryrestrictor).Thereislittleifa
3、nysamplepreparationandnochromatographicseparation.Theresponseoftheinstrumenttoanalytesinasampleisnearlyinstantaneous.Inaddition,theinstrumentisfieldtransportable,rugged,andrelativelyeasytooperateandmaintain.1.2Thismethodisapplicabletothedeterminationof
4、VOCsindiscretesamplestakentothelaboratoryandtoon-sitemeasurementandmonitoring.Itisbestsuitedforsemiquantitativescreening,forrepetitivequantitativeanalysisofpreviouslycharacterizedsamplesforpre-selectedanalytes,andforestablishingtheabsence/presenceofVOC
5、satthelimitofdetectionoftheoperatingconditionsemployed.Specialtyapplicationsincludeon-linedeploymentwithdirect-pushtechnologies,insitusampling,andcontinuousreal-timemonitoringofVOCs.1.3Themethodisnotsuitedtoidentifyingorquantitatingalargenumberofconsti
6、tuentsinhighlycomplexmixturesnortoquantitatingconstituentsattheisomericlevel.Identifyingunknownorunusualconstituentsincomplexmulti-componentmixturesisbetterachievedusingstandardgaschromatography/massspectrometrymethods.Thisprocedureisusuallynotapplicab
7、leifresultsarerequiredforindividualpositionalisomers(e.g.;o-,m-,orp-xylenes)orindividualgeometricisomers(e.g.,cis-ortrans-1,2-dichloroethenes)unlessuniqueoperatingconditionsaredevelopedanddemonstrated.Theprincipallimitationofthemethodistheneedtodemonst
8、ratetheabsenceofinterferinganalytesatthelevelsofconcernbeforequantitativeanalysiscanbeperformed.1.4Thismethodisespeciallyusefulfortheanalysisoflargenumbersofsamples,forscreeningsamples,foron-siteanalyses,andforapplicationsbenefittingfro
