3484397352 - lectrochemical Methods of Analysis...

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Unformatted text preview: lectrochemical Methods of Analysis Electrochemical Methods of Analysis Coulometric Methods of Analysis 1 1 6 008 Lecture # 9 &10 1 11/11 & 16/2008 oulometry Coulometry • An electrochemical method in which the current required to exhaustively oxidize y or reduce the analyte is measured. • Exhaustively means that the analyte is quantitatively oxidized or reduced at the working electrode. 2 oulometric Methods of Analysis Coulometric Methods of Analysis • Controlled-Potential Coulometry • ontrolled- urrent Coulometry Controlled Current Coulometry 3 Electrochemical Methods Static methods i =0 Dynamic methods i = 0 ( ) ( ) Potentiometry Controlled otential Controlled urrent y Potential Current Controlled Current Coulometry Variable Potential Fixed Potential Voltammetry Amperometry Controlled Potential Coulometry Stirred solutions Stripping Voltammetry Quiescent solutions 4 Hydrodynamic Voltammetry Polarography and Stationary Electrode Voltammetry Pulse Polarography and Voltammetry Cyclic Voltammetry ontrolled otential Coulometry Controlled-Potential Coulometry • A constant potential is applied to the electrochemical cell. ’ Q = nFN Faraday s Law: Q is the total charge in columbs e moles of analyte N the moles of analyte F Faraday’s constant, 96487 C mol-1 5 n is the number of electrons transferred per mole of analyte Controlled-Potential Coulometry Q = nFN Q = it e t is the electrolysis time e As current varies in “controlled potential coulometry”, e total charge will be given from: the total charge will be given from: t = t e Q = i(t) dt = 6 t = 0- Coulometry requires 100% current efficiency Controlled-Potential Coulometry...
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3484397352 - lectrochemical Methods of Analysis...

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