Square-wave voltammetry of the o-catecholâGe(IV) catalytic system after adsorptive preconcentration at a hanging mercury drop electrode (original) (raw)
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Analytica Chimica Acta, 1999
A model of the cathodic stripping process of an insoluble mercuric salt precipitated on the mercury electrode surface and complicated by adsorption of the reacting ligand, is developed under conditions of square-wave voltammetry (SWV). The adsorption isotherm of the reacting ligand is supposed to be linear. Theoretical relationships between the properties of the SW response and the parameters of the redox reaction as well as SW excitation signal are analyzed. Both reversible and quasireversible redox reactions are considered. The phenomena such as quasireversible maxima and splitting of the SW peak are discussed. The theoretical model is verified experimentally with the mercury/6-propyl-2-thiouracil system. The kinetic parameters of the redox reaction of mercury in the presence of 6-propyl-2-thiouracil in 1moldm−3 KNO3 are estimated as follows: standard rate constant ks=25±5s−1 and cathodic transfer coefficient α=0.6±0.1. The adsorption constant of 6-propyl-2-thiouracil on the mercury surface in 1moldm−3 KNO3 is estimated to be in the range: 0.1≤log(K/cm−1)≤1.2.
Electroanalysis, 2004
A comparative study of different types of cathodic stripping reactions under conditions of square-wave voltammetry is presented. Cathodic stripping processes involving reactions of second order as well as reactions coupled by adsorption of the reacting ligand are analyzed The inherent parameters, controlling the overall voltammetric behavior of each cathodic stripping electrode reaction are derived. The criteria for qualitative distinguishing of each mechanism are established as well as a methodology for redox kinetic measurements is proposed. The influence of the parameters of the excitation signal on the properties of the voltammetric response is analyzed in order to find optimal conditions for analytical application. The theoretical results are illustrated by the experiments with a series of uracil derivatives.