Electrochemical Study of the Pesticide Methidathion at a Mercury Electrode under Cathodic Stripping Mode

Methidathion, a non-systemic organophosphorous insecticide and acaricide is studied at the hanging mercury drop electrode under cathodic stripping mode by means of cyclic and square-wave voltammetry (SWV). Its electrode reaction is analyzed in the light of recent theory of cathodic stripping processes of insoluble salts of SWV. Its complex electrode mechanism is described by an electrode reaction of a second order, complicated by adsorption of methidathion molecules on the electrode surface involving lateral interactions between each other. Moreover, under specific experimental conditions the electrode mechanism can be additionally complicated by multilayer formation on the electrode surface, as well as by a chemical transformation following the cathodic stripping process of the methidathion- mercury salt. Following the mechanistic study of the electrode reaction, a method for quantitative determination of methidathion is proposed applying SWV

The Influence of Protonation on the Electroreduction of Bi (III) Ions in Chlorates (VII) Solutions of Different Water Activity

We examined the electroreduction of Bi (III) ions in chlorate (VII) solutions under varied protonation conditions of the depolariser using voltammetric and impedance methods. The results of the kinetic parameter correlation lead to the statement that the changes in the amount of chloric (VII) acid against the amount of its sodium salt in the supporting electrolytes of the low water activity have a significant influence on the rate of Bi (III) ion electroreduction. The increase of the concentration of chloric acid sodium salt, aswell as the chloric (VII) acid alone within the particular concentration of the supporting electrolyte, inhibits the process of Bi (III) ion electroreduction. It should be associated with the reorganisation of the structure of the double layer connected with the slow dehydration inhibited by ClO 4 − ions. The standard rate constants ks values with the increase of the chlorate (VII) concentrations for all the solutions examined of chlorates (VII) confirms the catalytic influence of the decrease of water activity on the process of Bi (III) ion electroreduction. The multistage process is confirmed by the non-rectilinear 1nkf=f(E) dependences

Reversible and Quasireversible Electron Transfer under Conditions of Differential Square-Wave Voltammetry

A theoretical analysis of reversible and quasireversible electrode reactions of a dissolved redox couple under conditions of the novel technique of differential square-wave voltammetry (DSWV) is presented. The technique is recently introduced as a hybrid form between differential pulse voltammetry (DPV) and square-wave voltammetry (SWV) as the two most advanced and competitive pulse-form voltammetric techniques for a purpose of unifying their advantages and further advancing both techniques in terms of analytical performances, mechanistic analysis, and electrode kinetics. The potential modulation of DSWV consists of potential steps and pulses providing a plethora of voltammetric curves, which enable in-depth characterization of the electrode reaction with a minimal set of measurements. Based on numerical simulations, a set of criteria for characterization and differentiation between reversible and quasireversible electrode reactions are established

Voltammetric behaviour and quantitative determination of pesticide iminoctadine

Publikacja w ramach programu Royal Society of Chemistry "Gold for Gold" 2014 finansowanego przez Uniwersytet ŁódzkiIminoctadine (IOD) was determined in spiked river water samples by square wave voltammetry (SWV) using a cyclic renewable silver amalgam film electrode (Hg(Ag)FE). It was found that the compound can act as an electrocatalyst. In Britton–Robinson buffer at pH 6.5 a signal connected with the catalytic hydrogen evolution reaction was detected at 1.8 V versus Ag/AgCl. Validation of the method was carried out. The LOD and LOQ have been estimated to be 2.6 10 9 mol L 1 and 8.5 10 9 mol L 1 , respectively

Characterizing electrode reactions by multisampling the current in square-wave voltammetry

A novel and simple methodology for characterization of electrode processes by square-wave voltammetry (SWV), considered as a complex repetitive double-step chronoamperometric experiment, is proposed. Specifically, the sampling of the current at the very end of each potential pulse, as common in conventional SWV, is replaced with a multisampling protocol during each potential pulse, resulting in generation of a series of corresponding multisampled SW voltammograms constructed out of a single measurement. The evolution of such voltammograms reflects the chronoamperometric properties of the current in the course of each potential pulse, thus being specific to electrode mechanism and electrode kinetics. The proposed methodology could serve as a basis for modification of common SWV mode in commercially available instrumentation for the purpose of an advanced characterization of electrode processes. The methodology is theoretically illustrated by the analysis of three kinetically controlled common electrode mechanisms, such as the electrode reaction of a solution resident and surface confined redox couples, as well as the regenerative catalytic electrode mechanism (EC’), while the experimental verification is done with the electrode reaction of Eu3+/Eu2+ and azobenzene/ hydrazobenzene redox couples