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1、METHOD7061AARSENIC(ATOMICABSORPTION,GASEOUSHYDRIDE)1.0SCOPEANDAPPLICATION1.1Method7061isanatomicabsorptionprocedurefordeterminingtheconcentrationofarsenicinwastes,mobilityprocedureextracts,soils,andgroundwater.Method7061Aisapprovedonlyforsamplematricesthatdonotcontainhighconcent
2、rationsofchromium,copper,mercury,nickel,silver,cobalt,andmolybdenum.Allsamplesmustbesubjectedtoanappropriatedissolutionsteppriortoanalysis.Spikedsamplesandrelevantstandardreferencematerialsareemployedtodeterminetheapplicabilityofthemethodtoagivenwaste.2.0SUMMARYOFMETHOD2.1Sample
3、sarepreparedaccordingtothenitric/sulfuricaciddigestionproceduredescribedinthismethod(Step7.1).Next,thearsenicinthedigestateisreducedtothetrivalentformwithtinchloride.Thetrivalentarsenicisthenconvertedtoavolatilehydrideusinghydrogenproducedfromazinc/hydrochloricacidreaction.2.2Th
4、evolatilehydrideissweptintoanargon-hydrogenflamelocatedintheopticalpathofanatomicabsorptionspectrophotometer.Theresultingabsorptionofthelampradiationisproportionaltothearsenicconcentration.2.3Thetypicaldetectionlimitforthismethodis0.002mg/L.3.0INTERFERENCES3.1Highconcentrationso
5、fchromium,cobalt,copper,mercury,molybdenum,nickel,andsilvercancauseanalyticalinterferences.3.2Tracesofnitricacidleftfollowingthesamplework-upcanresultinanalyticalinterferences.Nitricacidmustbedistilledoffbyheatingthesampleuntilfumesofsulfurtrioxide(SO3)areobserved.3.3Elementalar
6、senicandmanyofitscompoundsarevolatile;therefore,certainsamplesmaybesubjecttolossesofarsenicduringsamplepreparation.4.0APPARATUSANDMATERIALS4.1Beakerorequivalent-100-mL.4.2Electrichotplateorequivalent-adjustableandcapableofomaintainingatemperatureof90-95C.CD-ROM7061A-1Revision1Ju
7、ly19924.3.1Medicinedropper-Capableoffittingintoasize"0"rubberstopperanddelivering1.5mL.4.3.2Pear-shapedreactionflask-50-mL,withtwo14/20necks(ScientificGlassJM-5835orequivalent).4.3.3Gasinlet-outlettube-Constructedfromamicrocold-fingercondenser(JM-3325)bycuttingtheportionbelowthe
8、14/20ground-glassjoint.4.3.4Magneticstirrer-Toh
