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1、METHOD7063ARSENICINAQUEOUSSAMPLESANDEXTRACTSBYANODICSTRIPPINGVOLTAMMETRY(ASV)1.0SCOPEANDAPPLICATION1.1Thismethodisapplicableforlaboratorydeterminationsoffreedissolvedarsenicindrinkingwater,naturalsurfacewater,seawater,andindomesticandindustrialwastewater,andinsoilextracts
2、.1.2Arsenicconcentrationsinthelinearcalibrationrangeof0.3to300µg/Lmaybequantified.Theupperconcentrationrangemaybeextendedbysampledilution,bydecreasingtheanalytedepositiontime,orbyincreasingthestrippingcurrent.1.3Themethoddetectionlimitforfreearsenicisabout0.1µg/L.1.4Theme
3、thodisequallysensitiveforAs(III)andAs(V).2.0SUMMARYOFMETHODStandardsandsamplesaremadeacidicandrenderedelectricallyconductivebyaddinghydrochloricacid.Freedissolvedarsenicisquantifiedbyanodicstripping,atapotentialof+145mVwithrespecttothesaturatedcalomelelectrode(SCE),fromac
4、onditionedgoldmetalfilmdepositedonaglassycarbonelectrode(GCE).3.0INTERFERENCES3.1Dissolvedantimonyandbismutharepositiveinterferences.Dissolvedcopper,atconcentrationsgreaterthan1mg/L,isalsoapositiveinterference.3.2Turbidsamplesmustbefilteredthroughaborosilicateglassfilterw
5、ith0.45-µmporestoprecludephysicalerosionoftheGCEgoldfilm.3.3SomewetdepositionsamplesmayhaveinsufficientelectricalconductivityforproperoperationoftheASVinstrumentation.Thisproblemisobviatedbymakingthesolutions2MinHCl.3.4Whentheanalysisisperformedaccordingtotheinstructionsg
6、ivenbelow,thefollowingions,compounds,andsampleconditionsareknownnottointerferewiththequantitationofarsenic;seawatersalts,water-solubleorganiccompoundssuchassugarsandtannicacid,anddissolvedcopperatconcentrationslessthan100timesthearsenicconcentration.4.0.APPARATUSANDMATERI
7、ALS4.1ASVinstrumentation(RadiometerTraceLab,orequivalent),includingpotentiostat,electrodes,stirrer,samplestand,polyethylenesamplecups,andGCEpolishingpowder.4.2Computer,asrecommendedbyASVinstrumentationmanufacturer.CD-ROM7063-1Revision0December19964.3Plasticsyringeandanylo
8、nsyringefilterwith0.45-µmpores.4.4Adjustablepipetterswithpolyethylenetips.4.5pHmeterorpHindicato
