Submicromolar Analysis with Rotating and Hydrodynamically Modulated Disk Electrodes

The sensitivity limits of rotating disk electrode (RDE) voltammetry have been critically evaluated. At the RDE, either direct potential scanning or rotation speed variation at constant potential are thoroughly competitive with modern dropping mercury electrode (DME) techniques. Where non-ideal conditions exist because of interference from surface processes or supporting electrolyte reactions, the technique of hydrodynamic modulation at the rotating disk electrode (HMRDE) can restore the RDE sensitivity limit to that of the nearly ideal situation. Even charging current effects can be almost totally rejected by this technique. The RDE and HMRDE methods have been applied to concentrations as low as 5 × 10^-8M. The systems studied at micro- and submicromolar levels were nitrobenzene and Tl(I) at amalgamated gold, quinhydrone and Hg(II) at gold, quinhydrone at platinum, Fe(II)— Fe(III) and Hg(II) at graphite, and sulfide at silver.