EPA METHOD 3520C Continuous Liquid-Liquid Extraction

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1、METHOD3520CCONTINUOUSLIQUID-LIQUIDEXTRACTION1.0SCOPEANDAPPLICATION1.1Thismethoddescribesaprocedureforisolatingorganiccompoundsfromaqueoussamples.ThemethodalsodescribesconcentrationtechniquessuitableforpreparingtheextractfortheappropriatedeterminativestepsdescribedinSec.4.3ofChapterFour.1.

2、2Thismethodisapplicabletotheisolationandconcentrationofwater-insolubleandslightlysolubleorganicsinpreparationforavarietyofchromatographicprocedures.1.3Method3520isdesignedforextractionsolventswithgreaterdensitythanthesample.Continuousextractiondevicesareavailableforextractionsolventsthata

3、relessdensethanthesample.Theanalystmustdemonstratetheeffectivenessofanysuchautomaticextractiondevicebeforeemployingitinsampleextraction.1.4Thismethodisrestrictedtousebyorunderthesupervisionoftrainedanalysts.Eachanalystmustdemonstratetheabilitytogenerateacceptableresultswiththismethod.2.0S

4、UMMARYOFMETHOD2.1Ameasuredvolumeofsample,usually1liter,isplacedintoacontinuousliquid-liquidextractor,adjusted,ifnecessary,toaspecificpH(seeTable1),andextractedwithorganicsolventfor18-24hours.2.2Theextractisdried,concentrated(ifnecessary),and,asnecessary,exchangedintoasolventcompatiblewith

5、thecleanupordeterminativemethodbeingemployed(seeTable1forappropriateexchangesolvents).3.0INTERFERENCES3.1RefertoMethod3500.3.2Thedecompositionofsomeanalyteshasbeendemonstratedunderbasicextractionconditionsrequiredtoseparateanalytes.Organochlorinepesticidesmaydechlorinate,phthalateestersma

6、yexchange,andphenolsmayreacttoformtannates.ThesereactionsincreasewithincreasingpH,andaredecreasedbytheshorterreactiontimesavailableinMethod3510.Method3510ispreferredoverMethod3520fortheanalysisoftheseclassesofcompounds.However,therecoveryofphenolsmaybeoptimizedbyusingMethod3520andperformi

7、ngtheinitialextractionattheacidpH.4.0APPARATUSANDMATERIALS4.1Continuousliquid-liquidextractor-Equippedwithpolytetrafluoroethylene(PTFE)orglassconnectingjointsandstopcocksrequiringnolubrication(Kontes584200-0000,584500-0000,583250-0000,orequivalent).CD-ROM3520C-1Revi