Diagnostics of Anodic Stripping Mechanisms under Square-Wave Voltammetry Conditions Using Bismuth Film Substrates

A mechanistic study to provide diagnostics of anodic stripping electrode processes at bismuth-film electrodes is presented from both theoretical and experimental points of view. Theoretical models for three types of electrode mechanisms are developed under conditions of square-wave voltammetry, combining rigorous modeling based on integral equations and the step function method, resulting in derivation of a single numerical recurrent formula to predict the outcome of the voltammetric experiment. In the course of the deposition step, it has been assumed that a uniform film of the metal analyte is formed on the bismuth substrate, in situ deposited onto a glassy carbon electrode surface, without considering mass transfer within either the bismuth or the metal analyte film. Theoretical data are analyzed in terms of dimensionless critical parameters related with electrode kinetics, mass transfer, adsorption equilibria, and possible lateral interactions within the deposited metal particles. Theoretical analysis enables definition of simple criteria for differentiation and characterization of electrode processes. Comparing theoretical and experimental data, anodic stripping processes of zinc(II), cadmium(II), and lead(II) are successfully characterized, revealing significant differences in their reaction pathways. The proposed easy-to-perform diagnostic route is considered to be of a general use while the bismuth film exploited in this study served as a convenient nonmercury model substrate surface

Diagnostics of Anodic Stripping Mechanisms under Square-Wave Voltammetry Conditions Using Bismuth Film Substrates

A mechanistic study to provide diagnostics of anodic stripping electrode processes at bismuth-film electrodes is presented from both theoretical and experimental points of view. Theoretical models for three types of electrode mechanisms are developed under conditions of square-wave voltammetry, combining rigorous modeling based on integral equations and the step function method, resulting in derivation of a single numerical recurrent formula to predict the outcome of the voltammetric experiment. In the course of the deposition step, it has been assumed that a uniform film of the metal analyte is formed on the bismuth substrate, in situ deposited onto a glassy carbon electrode surface, without considering mass transfer within either the bismuth or the metal analyte film. Theoretical data are analyzed in terms of dimensionless critical parameters related with electrode kinetics, mass transfer, adsorption equilibria, and possible lateral interactions within the deposited metal particles. Theoretical analysis enables definition of simple criteria for differentiation and characterization of electrode processes. Comparing theoretical and experimental data, anodic stripping processes of zinc(II), cadmium(II), and lead(II) are successfully characterized, revealing significant differences in their reaction pathways. The proposed easy-to-perform diagnostic route is considered to be of a general use while the bismuth film exploited in this study served as a convenient nonmercury model substrate surface

Studies on Electrode Processes in Stripping Analysis Using Square-Wave Voltammetry: Theory and Application

This paper presents mechanistic studies on electrode processes in stripping trace and ultratrace analysis under square-wave voltammetry conditions from both theoretical and experimental points of view. Besides adsorptive stripping and cathodic stripping mechanisms [1], a special attention is given to the anodic stripping processes at bismuth-film electrodes [2]. Several electrode mechanisms are analyzed, including those coupled with adsorption equilibria and lateral interactions of selected metal analytes within the deposited electroactive film. An attempt is made to identify a critical set of voltammetric properties upon which diagnostic criteria can be established for differentiation between particular electrode mechanisms. Theoretical data are analyzed in terms of dimensionless critical voltammetric parameters related to electrode kinetics, mass transfer, adsorption equilibria, and possible lateral interactions. Several strategies for electrode kinetic measurements are presented. The study mainly focuses on the role of the height of the potential pulses used in square-wave voltammetry that enables kinetic measurements at a constant scan rate. Theoretical considerations outlined are illustrated using experimental data collected at bismuth-film electrodes

Mechanisms and kinetics of electrode processes at bismuth and antimony film and bare glassy carbon surfaces under square-wave anodic stripping voltammetry conditions

Mechanism and kinetics of anodic stripping electrode processes of Zn(II), Cd(II) and Pb(II) at bismuth (BiFE) and antimony (SbFE) film as well as bare glassy carbon (GCE) electrodes have been studied with respect to our recent published theoretical considerations developed for square-wave voltammetry (SWV). Mechanistic aspects of electrode reactions have been elucidated by a qualitative comparison of simulated and experimental data for three different electrode reaction mechanisms, i.e. simple anodic stripping mechanism, anodic stripping mechanism coupled with adsorption of metal analyte ions, and mechanism affected by interactions within the particles of the metal deposit on the electrode surface. The electrode kinetics has been estimated by the method of quasireversible maximum and by analyzing the peak potential separation between forward and backward SW components, under variation of the SW amplitude. Electrode mechanisms and kinetics are different at bismuth compared to antimony film electrodes. The electrode reactions of Pb(II) and Cd(II) at BiFE involve adsorption phenomena, while electrode processes of all three analytes are free of adsorption at SbFE. At BiFE, the electron transfer standard rate constants of all three analytes are quite comparable, ranging within the interval from 1 to 3 cm s−1. At SbFE the electrode kinetics of Cd(II) and Pb(II) are almost the same, while the electrode reaction of Zn(II) is significantly slower. Our results showed that the kinetics of all examined electrode reactions are slower at SbFE as compared to those observed at BiFE