It has become common practice to estimate the numbers of electrons (n, eq mol−1) transferred in faradaic reactions at rotated disk electrodes (RDEs) from the slope of plots of reciprocal current (1/I) vs. reciprocal square root of rotational velocity (1/ω1/2). This practice is based on the Koutecký‐Levich equation derived for a one‐step electron‐transfer mechanism. Furthermore, the intercept of the Koutecký‐Levich plot is assumed to be a reciprocal function of the heterogeneous rate constant (kh, cm s−1) for the electron‐transfer process. In this review, we examine the validity of the practice of estimating values of n and kh for various multi‐step mechanisms at RDEs.

No abstract

Virtually all organic compounds and numerous inorganic compounds are predicted from thermodynamics to be oxidized at potentials accessible at commonly used solid electrodes in aqueous media by reactions which require transfer of oxygen from H,O to the oxidation products. These anodic reactions are usually kinetically inhibited because of their complexity. Progress is summarized to develop electrocatalytic processes for anodic detection in flowing aqueous solutions.Pulsed amperometric detection at Pt electrodes is applicable for the sensitive detection of the HCOH group in all alcohols, polyalcohols and carbohydrates, the nitrogen in amines, amino acids and aminoglycosides, and sulphur in most inorganic and organic compounds. Pure and doped lead dioxide electrodes are described for amperometric detection at constant potential.The voltammetric response of electrocatalysed oxygen-transfer reactions is dictated by the potential dependence of the process transferring oxygen from H,O to the electrode surface, so that attempts at voltammetric resolution of mixtures are not generally effective. The most useful analytical application of the electrocatalysed processes for mixtures is in the form of amperometric detection in liquid-chromatographic systems.Electrochemical (EC) detection in miniature flow-through cells applied in conjunction with high-performance liquid-chromatographic (LC) separations joins together the analytical strengths of both component techniques. EC detection is highly sensitive at moderately low cost, whereas LC, in its numerous forms, is far superior to electroanalytical voltammetry in resolving power for analysis of complex mixtures. It is the goal of research summarized here to achieve maximum electrocatalytic activity for anodic EC detection, even at the sacrifice of voltammetric selectivity.