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Chapter10-ElectrochemicalAnalysis-Potentiometry1
PotentiometryAnalyticalmethodbasedonmeasuringthepotentialofelectrochemicalcellswithoutdrawingappreciablecurrentpHmeterIon-selectivemembraneelectrodes(ISEs)Rapidanalysis2
Generalprinciples3
Liquid-junctionpotential(diffusionpotential)Tendencyofmigrationofions(hightolowconcentration)highconcentrationlowconcentrationDiffusionratesvarySeparationofchargeElectricfieldCounteractdifferentmobilitiesSaturatedKClsaltbridge4
Classification(IUPAC):metalelectrodesClass0:Inertmetalsusedinoxidation-reductionelectrolyticcells.Idealinertmaterialsexchangeelectronsreversiblywiththeelectrolytecomponentsandarenotsubjecttooxidationorcorrosionthemselves,i.e.,“ideally”polarizableelectrodes.Class1:Reversiblemetal/metalion(ionexchangingmetalsbathedinelectrolytescontainingtheirownions),forexampleAg/Ag+.Class2:Reversiblemetal/metalionwithsaturatedsaltofthemetalionandexcessanionX-,forexampleAg/AgX/X-.Class3:Reversiblemetal/metalsaltorsolublecomplex/secondmetalsaltorcomplexandexcesssecondcation,forexamplePb/Pb-oxalate/Ca-oxalate/Ca2+orHg/HgEDTA2-/CaEDTA2-/Ca2+5
Classification(IUPAC):otherelectrodesAtagas-electrodeonecomponentoftheredoxcoupleisinthegaseousstate.Ion-selectiveelectrodes(ISEs)basedonthinfilmsorselectivemembranesasrecognitiveelementsareequivalenttootherhalf-cellsChemicallymodifiedelectrodes(CME)/publications/analytical_compendium/Cha08sec31.pdf6
Typesofion-selectivemembraneelectrodesCrystalline SinglecrystalLaF3forF- PolycrystallineormixedcrystalAg2SforS2-orAg+Noncrystalline GlassH+orNa+ LiquidionexchangerforCa2+ ImmobilizedliquidinarigidpolymerPVCforCa2+7
Propertiesofion-selectivemembranesMinimalsolubilityElectricalconductivitySelectivereactivity8
Compositionandstructureofglassmembranes9
Silicateglassstructure10
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