Fundamental Principles of Voltammetry

Information about suitable working potentials for the amperometric detection of electroactive species is obtained in voltammetric experiments. The term voltammetry refers to the investigation of current-voltage curves in dependence on the electrode reactions, and the concentrations, and the exploitation of these dependences for analytical chemistry. Among the different types of voltammetry. 

The chlorides, chlorates, and perchlorates of alkali and alkaline-earth metals, alkali hydroxides, and carbonates as well as quaternary ammonium compounds are utilized as supporting electrolytes. 

In general, the following reaction occurs in an amperometric detection  

A transfers n electrons to the working electrode and is oxidized to B. The relation between the concentration of oxidized and reduced species and the applied potential is described by the Nernst equation  

Equilibrium concentrations of both species at the electrode surface Standard potential, at which the concentrations of A and B are equal. (Because chromatography is carried out at low concentrations, concentrations may be used instead of activities in Eq. (8.34) in good approximation.) 

Two kinds of current are generated during the oxidation of A to B the charging current and the Faraday current. The charging current results from the charging of the interface between the electrode and the bulk solution, which acts as a condensator. The Faraday current represents the electron transfer in the oxidation of A to B. As illustrated in Fig. 7-6, the drop in the charging current follows an exponential time law. The drop in the Faraday current over time is described by the equation of Cotrell  

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