Abstract
This method of analysis is based upon a differential amperometric approach. It requires a constant sample flow rate and a constant input current to the cell. Diffusion, convection control of the transport of the electroactive species to the working electrode establishes the permissible current passed by the working electrode. Control of the potential of the working electrode, and thereby its specificity of reaction, is achieved by means of a massive, reversible bipolar electrode. The working electrode is wired to ground while the bipolar electrode is held at virtual ground at the summing point of an operational amplifier wired in a current to voltage configuration. The difference current between the constant current input to the cell and the current demanded by the working electrode will be supplied or absorbed by the bipolar electrode circuit. Ordinarily the constant input current is adjusted initially so as to bring the bipolar current to zero at the desired set-point concentration. Thus the sign and magnitude of the output voltage will follow the change in concentration of the electroactive species above or below the set-point concentration. The method thereby enjoys the advantages of specificity and lack of special endpoint detection characteristic of controlled potential electrolysis together with the speed and simplicity of constant current electrolysis.
Published Version
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