Designation:D6317−15StandardTestMethodforLowLevelDeterminationofTotalCarbon,InorganicCarbonandOrganicCarboninWaterbyUltraviolet,PersulfateOxidation,andMembraneConductivityDetection1ThisstandardisissuedunderthefixeddesignationD6317;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thistestmethodcoversthedeterminationoftotalcarbon(TC),inorganiccarbon(IC),andtotalorganiccarbon(TOC)inwaterintherangefrom10to1000µg/Lofcarbon.ThismethodisforlaboratoryorgrabsampleapplicationsandhasbeensubjectedtoaninterlaboratorystudyundertheguidelinesofD2777.TestMethodD5997canbeusedforon-linedeterminations.Thetestmethodutilizespersulfateorultravioletoxidationoforganiccarbon,orbothcoupledwithaCO2selectivemembranetorecovertheCO2intodeionizedwater.Thechangeinconductivityofthedeionizedwaterismeasuredandrelatedtocarbonconcentrationintheoxidizedsample.Inorganiccarbonisdeterminedinasimilarmannerwithouttheoxidationstep.Inbothcases,thesampleisacidifiedtofacilitateCO2recoverythroughthemembrane.TherelationshipbetweentheconductivitymeasurementandcarbonconcentrationisdescribedbyasetofchemometricequationsforthechemicalequilibriumofCO2,HCO3–,andH+,andtherelationshipbetweentheionicconcentrationsandtheconduc-tivity.Thechemometricmodelincludesthetemperaturede-pendenceoftheequilibriumconstantsandthespecificconduc-tancesresultinginlinearresponseofthemethodoverthestatedrangeofTOC.SeeTestMethodD4519foradiscussionofthemeasurementofCO2byconductivity.1.2Thistestmethodhastheadvantageofaveryhighsensitivitydetectorthatallowsverylowdetectionlevelsonrelativelysmallvolumesofsample.Also,useoftwomeasure-mentchannelsallowsdeterminationofCO2inthesampleindependentlyoforganiccarbon.IsolationoftheconductivitydetectorfromthesamplebytheCO2selectivemembraneresultsinaverystablecalibration,withminimalinterference...
