1492Ch25

Manahan,StanleyE.ANALYSISOFWASTESANDSOLIDSEnvironmentalChemistryBocaRaton:CRCPressLLC,200025ANALYSISOFWASTESANDSOLIDS____________________________________________________25.1.INTRODUCTIONTheanalysisofhazardouswastesofvariouskindsforavarietyofpotentiallydangeroussubstancesisoneofthemostimportantaspectsofhazardouswastemanagement.1Theseanalysesareperformedforanumberofreasonsincludingtracingthesourcesofwastes,assessingthehazardsposedbythewastestosurround-ingsandtowasteremediationpersonnel,anddeterminingthebestmeansofwastetreatment.Thischapterisabriefoverviewofseveralofthemainconsiderationsappliedtotheanalysisofwastes.Here,wastesarebroadlydefinedtoincludeallkindsofsolids,semisolids,sludges,liquids,contaminatedsoils,sediments,andotherkindsofmaterialsthatareeitherwastesthemselvesorarecontaminatedbywastes.Forthemostpart,thesubstancesdeterminedaspartofwasteanalysis,theanalytes,aremeasuredbytechniquesthatareusedforthedeterminationofthesameanalytesinwater(seemethodsdescribedinChapter24)and,toalesserextent,inair.However,thepreparationtechniquesthatmustbeemployedforwasteanalysisareusuallymorecomplexthanthoseusedforthesameanalytesinwater.Thatisbecausethematricesinwhichthewasteanalytesarecontainedareusuallyrelativelycomplicated,whichmakesitdifficulttorecoveralltheanalytesfromthewasteandwhichintroducesinterferingsubstances.Asaresult,thelowerlimitsatwhichsubstancescanbemeasuredinwastes(thepracticalquantitationlimit,seeSection24.1)areusuallymuchhigherthaninwater.Thereareseveraldistinctstepsintheanalysisofawaste.Comparedtowater,wastesareoftenhighlyheterogeneous,whichmakesthefirststep,collectionofrepresentativesamples,difficult.Whereaswatersamplescanoftenbeintroducedintoananalyticalinstrumentwithminimalpreparation,theprocessingofhazardouswastestogetasamplethatcanbeintroducedintoaninstrumentisoftenrelativelycomplicated.Suchprocessingcanconsistofdilutionofoilysampleswithanorganicsolvent,extractionoforganicanalytesintoanorganicsolvent,evolutionandcollect-ionofvolatileorganiccarbonanalytes,ordigestionofsolidswithstrongacidsandoxidantstoextractmetalsforatomicspectrometricanalysis.Theproductsofthese©2000CRCPressLLCprocessesmustoftenbesubjectedtorelativelycomplicatedsamplecleanupproced-urestoremovecontaminantsthatmightinterferewiththeanalysisordamagetheanalyticalinstrument.Overanumberofyears,theU.S.EnvironmentalProtectionAgencyhasdevel-opedspecializedmethodsforthecharacterizationofwastes.ThesemethodsaregiveninthepublicationentitledTestMethodsforEvaluatingSolidWaste,Physical/ChemicalMethods,whichisperiodicallyupdatedtokeepitcurrent.2Becauseofthedifficultandexactingnatureofmanyoftheproceduresinthisworkandbecauseofthehazardsassociatedwiththeuseofreagentssuchasstrongacidsandoxidantsusedforsampledigestionandsolventsusedtoextractorganicanalytes,anyoneattemptinganalysesofhazardouswastematerialsshouldusethisresourceandfollowprocedurescarefullywithspecialattentiontoprecautions.“SW-846,”asitiscommonlyknown,isavailableinaconvenientCD/ROMformaspartofacomprehensivesummaryofenvironmentalanalyticalmethods.325.2.SAMPLEDIGESTIONInordertoanalyzeasolidwastesamplebyflameatomicabsorptionspectro-scopy,graphitefurnaceabsorptionspectroscopy,inductivelycoupledargonplasmaspectroscopy,orinductivelycoupledargonplasmamassspectrometry,thesamplemustfirstbedigestedtogettheanalytemetalsinsolution.Digestiondissolvesonlythosefractionsofmetalsthatcanbeputintosolutionunderrelativelyextremecon-ditionsandthereforeenablesmeasurementofavailablemetals.Itshouldbenotedthatsampledigestionproceduresgenerallyusehighlycorrosive,dangerousreagentswhicharestrongacidsandstrongoxidants.Therefore,digestionshouldbecarriedoutonlybycarefullytrainedpersonnelusingtheproperequipment,includingfumehoodsandadequatepersonnelprotection.EPAMethod3050isaprocedureforaciddigestionofsediments,sludges,andsoils.Asampleofupto2gistreatedwithamixtureofnitricacidandhydrogenperoxide;thesampleisthenrefluxedwitheithercon.HNO3orcon.HCl,thenrefluxedwithdiluteHCl,filtered,andthefiltrateanalyzedformetals.Microwaveheatingcanbeusedtoassistthedigestionofsamples.Theprocedureforthedigestionofaqueousliquidsconsistsofmixinga45mLsamplewith5mLofconcentratednitricacid,placingitinafluorocarbon(Teflon)digestionvessel,andheatingfor20minutes.Afterdigestioniscomplete,thesampleiscooled,solidsareseparatedbyfiltrationorcentrifugation,andtheliquidremainingisanalyzedbytheappropriateatomicspectrometrictechnique.Method3052isaprocedureformicrowaveassistedaciddigestionofsiliceousandorganicallybasedmatrices.Itcanbeusedonavarietyofkindsofsamplesincludingbiologicaltissues,oils,oil-contaminatedsoils,sediments,sludges,andsoil.Thismethodisnotappropriateforanalysesofleachablemetals,butisusedformeasurementoftotalmetals.Asampleofupto0.5gisdigestedwithmicrowaveheatingfor15minutesinanappropriatefluorocarbonpolymercontainerinanappropriateacidmixture.Commonly,thereagentsemployedareamixtureof9mLofcon.nitricacidand3mLhydrofluoricacid,althoughotheracidmixturesemployingreagentssuchascon.HClandhydrogenperoxidemaybeused.Thesampleisheatedinthemicrowaveovento1