A Simplified Model of Reactant Adsorption in Normal Pulse Voltammetry

Normal pulse voltammetry and chronoamperometry of reversible electro-oxidation complicated by the reactant adsorption on the surface of stationary, planar electrode is investigated theoretically. A simple model of chronoamperometry is compared with a rigorous model of voltammetry. The solution of former is analytical, but it applies to the linear isotherm. However, it explains the origin of maximum of the current-potential curves and its relationship with the pulse duration. The second model is based on digital simulation and describes voltammograms that correspond to the Langmuir isotherm. The accumulation of the reactant during the potential scan is calculated. The limits of electroanalytical application of the normal pulse voltammetry are determined. This work is licensed under a Creative Commons Attribution 4.0 International License

Simulation of Square Wave Voltammetry of Three Step Redox Reactions on Spherical Electrodes

The theory of three step electrode reaction is developed for square wave voltammetry on stationary spherical electrodes. It was assumed that all electroactive species are solution soluble. The dependence of the response on the thermodynamic stability of intermediates, on the electrode radius and the scan direction is investigated for the fast and reversible electrode reactions. The criterion of reversibility is postulated. Furthermore, the influence of electrode kinetics on the response was calculated for the cathodic and anodic scan directions. The difference in responses caused by the variation of scan direction is an indication of multiple electron transfers. The method for the estimation of transfer coefficient is demonstrated. This work is licensed under a Creative Commons Attribution 4.0 International License

Theory of Square-wave Voltammetry of Kinetically Controlled Two-step Electrode Reactions

An influence of electron transfer kinetics on square-wave voltammograms of two-step electrode reaction is investigated theoretically. A phenomenon of “kinetic burden” of potential inversion is described for the case of equal kinetic parameters. A linear relationship between standard rate constant and the difference between standard potentials of the second and the first charge transfers is demonstrated for the reactions with thermodynamically unstable intermediate. (doi: 10.5562/cca2126

A simple method for detection of manganese in marine sediments

Microparticles of sediment are mechanically transferred to the graphite electrode surface and the presence of manganese oxyhydroxides is detected by square-wave voltammetry in 0.1 M oxalic acid. After preelectrolysis at -2 V vs. Ag/AgCl, a characteristic stripping peak appears at -0.60 V. Following oxidation at 0.9 V, the response is dominated by a peak at 0.32 V

Staircase Voltammetry using Rotating Disk Electrode

A theory of staircase voltammetry on the rotating disk electrode is developed. The simulation is based on the method of variable diffusion layer thickness. Critical parameters that define the form of responses are calculated

A Simple Method for Detection of Manganese in Marine Sediments

Microparticles of sediment are mechanically transferred to the graphite electrode surface and the presence of manganese oxyhydroxides is detected by square-wave voltammetry in 0.1 M oxalic acid. After preelectrolysis at -2 V vs. Ag/AgCl, a characteristic stripping peak appears at -0.60 V. Following oxidation at 0.9 V, the response is dominated by a peak at 0.32 V

Theory of Square Wave Voltammetry of Two Reversible Electrode Reactions Connected by The Reversible Chemical Reaction

A theory of the mechanism that consists of two reversible electrode reactions coupled by kinetically controlled reversible chemical reaction is developed for square wave voltammetry on stationary planar electrode. The influences of frequency and the concentration of electro-inactive chemical reactant on the responses are investigated for thermodynamically stable intermediate. The limits of three types of responses are calculated and the formula for the estimation of the forward rate constant of chemical reaction is proposed

The UV and VIS Absorption Spectra of Jatrorubine

The absorption spectra of water, methanolic, ethanolic and propanolic solutions of jatrorubine in the VIS and UV spectral range were recorded. The acidity and the alkalinity of the solutions were changed in the wide range from pH = 2 to pH = 13 by the addition of KOH and HCl in the solutions. From the influence of pH on the shapes of the absorption curves, it was concluded that jatrorubine exists as quaternary aminic cation in the acidic medium and as the resonance dipole molecula in the basic media, but no evidence for the existence of carbinolic form was found. The results were compared with the literature data

Kinetika površinske redoks reakcije 2-hidroksi-5-[(4-sulfofenil)azo]benzojeve kiseline

The standard surface redox reaction rate constant of the quasireversible electroreduction of 2-hydroxy-5-[(4-sulfophenyl)azo]benzoic acid adsorbed on the static mercury drop electrode has been determined as ks = 24 (± 6) s–1 using the method of split square-wave voltamograms.Rabeći metodu rascijepljenih pravokutnovalnih voltamograma, određena je standardna konstanta brzine površinske redoks reakcije (ks = 24 (± 6) s–1) kvazireverzibilne elektroredukcije 2-hidroksi-5-[(4-sulfofenil)azo]benzojeve kiseline adsorbirane na površini statične živine kapi