Voltammetry

Modified: November 28, 2006

Introduction to Electrolytic Methods of Analysis

  • review of electrolytic cells
  • selective electrolysis in a mixture of electroactive species
  • definition of working and counter electrodes
  • a brief overview of the bulk electrolytic methods of analysis: coulometry & electrogravimetry. Advantages compared to other titrimetric and gravimetric methods.

Electrode Polarization in Electrolytic Cells

  • i-E plot showing electrode polarization in an electrolytic cell
  • types of electrode polarization: mass-transfer (concentration) and electron-transfer (kinetic)
  • mass transfer of ions in an electrolytic cell: convection, diffusion, ion migration.
  • reduction/elimination of analyte ion migration in electrolytic cells.

General Principles of Voltammetry

  • Fick's First Law of Diffusion, and its importance in voltammetry
  • Clark oxygen electrode (an amperometric sensor) and how it works. Factors affecting the signal.
  • generalization of the Clark electrode to voltammetry: controlled variable, measured variable, effect of analyte concentration, other factors that can affect measurement

Voltammetry Signal Theory

  • hydrodynamic voltammetry. Origin of stagnant "depleted" layer of analyte. Effect of analyte on limiting current.
  • effect of WE potential on current: voltammograms in hydrodynamic voltammetry
  • diffusion-limited current for a planar WE in unstirred solution: the Cottrel equation

Electrodes in Voltammetry

  • types of electrodes used in voltammetry
  • 3-electrode potentiostat to control WE during electrolysis
  • Hg drop electrodes: HMDE, DME and SMDE
  • advantages of Hg drop electrodes

Polarography

  • diffustion-limited current for a DME in an unstirred solution: the Ilkovic equation
  • Faradaic and non-Faradaic currents in polarography
  • advantage of SMDE over the DME
  • basic types of polarography: DCP, sampled DCP, NPP, DPP
  • square-wave voltammetry
  • principles of stripping voltammetry
  • comparison of methods in terms of precision and sensitivity