EPA METHOD 6500 Dissolved Inorganic Anions in Aqueous

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1、METHOD6500DISSOLVEDINORGANICANIONSINAQUEOUSMATRICESBYCAPILLARYIONELECTROPHORESIS1.0SCOPEANDAPPLICATION1.1Thistestmethodisapplicablefordeterminationofthedissolvedinorganicanions;fluoride,bromide,chloride,nitrite,nitrate,ortho-phosphate,andsulfateinaqueousmatricesusingcapillaryionelectropho

2、resiswithindirectUVdetection.1.2Thistestmethodisapplicabletodrinkingwater,wastewaterandgroundwaterfortheanalysisofinorganicanionsintheconcentrationrangeof0.1to50mg/L,exceptforfluoride,whichhasarangeof0.1to25mg/L.Itistheuser'sresponsibilitytoensuretheapplicabilityofthistestmethodforotheran

3、ionconcentrationrangesandotheraqueoussamplematrices.1.3Capillaryionelectrophoresisprovidesasimultaneousseparationanddeterminationofseveralinorganicanionsusingnanolitersofsampleinasingleinjection.Only500µLofsampleisrequiredtofilltheanalysisvial.Analysistimeislessthan5minutes.2.0SUMMARYOFME

4、THOD2.1Capillaryionelectrophoresis(Figs.1-4)isafreezoneelectrophoretictechniqueoptimizedfortheanalysisofanionswithmolecularweightslessthan200.Theanionsmigrateandareseparatedaccordingtotheirmobilityintheelectrolytewhenanelectricalfieldisappliedthroughtheopentubularfusedsilicacapillary.Thee

5、lectrolyte'selectroosmoticflow(EOF)modifierdynamicallycoatstheinnerwallofthecapillary,changingthesurfacetoanetpositivecharge.ThisreversalofwallchargereversesthenaturalEOF.ThemodifiedEOFincombinationwithanegativepowersupplyaugmentsthemobilityoftheanalyteanionstowardstheanodeanddetectorachi

6、evingrapidanalysistimes.Cationsmigrateintheoppositedirectiontowardsthecathodeandareremovedfromthesampleduringanalysis.WaterandotherneutralspeciesmovetowardthedetectoratthesamerateastheEOF.Theneutralspeciesmigrateslowerthantheanalyteanionsanddonotinterferewithanionanalysis(Figs.2and3).2.2T

7、hesampleisintroducedintothecapillaryusinghydrostaticsampling.Theinletofthecapillary,containingelectrolyte,isimmersedinthesampleandthesampleraised10cmfor30secondswhere36nanolitervolumesaresiphonedintothecapillary.Aftersampleloading,thecapillaryisimmediatelyimmersedba