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In this paper a theoretical study of stripping processes at planar electrodes under conditions of square‐wave voltammetry is presented. A mechanistic examination for cathodic stripping electrode mechanisms, a simple anodic striping mechanism, and anodic stripping mechanisms coupled with adsorption equilibrium of the analyte are discussed using varying square‐wave amplitudes. The methodologies described here use two typical features: the peak potential separation of square‐wave components and the amplitude‐based quasireversible maximum. Both methods can be applied at a constant frequency, i. e., constant scan rate. The received data are combined with the critical parameters of electrode reaction kinetics. Thus, the established methodologies allow for a simple kinetic characterization. The received diagnostic criteria are verified with experiments at a glassy carbon electrode for lead ions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electrochemical faradaic spectroscopy and differential square wave voltammetry used for the first time. • Electrochemical detection of H 2 O 2 in gaseous phase. • Deep mechanistic study for reduction of H 2 O 2 on electrode surface in the presence of Cu ions. • Cu ions are active materials for detection and PAA is excellent for gaseous H 2 O 2 absorption. A comprehensive voltammetric investigation into the electrocatalytic electrode mechanism for the reduction of hydrogen peroxide in an aqueous polyacrylic acid solution, in the presence of Cu2+ ions, is presented. The primary objective is to lay the groundwork for the development of a straightforward electrochemical sensor for the detection of gaseous H 2 O 2. Various electrode reaction pathways have been observed depending on the potential applied to the glassy carbon electrode. At potentials approximately −0.400 V vs. Ag/AgCl (3 mol L−1 KCl), an electrochemical reduction of H 2 O 2 occurs. In this context, the Cu2+/Cu+ redox couple, stabilized by polyacrylic acid, acts as a redox mediator, following the EC' reaction scheme. Additionally, a complex Fenton-like spontaneous redox chemistry takes place between Cu2+/Cu+ and H 2 O 2 within the bulk of the polyacrylic aqueous solution. This results in the generation of a variety of reactive oxygen species (ROS), with the superoxide anion and hydroxyl radical being the most probable intermediates. The electrochemical reduction of ROS species effectively recycles H 2 O 2 near the electrode surface, constituting an electrocatalytic mechanism of the second order. This particular electrocatalytic process is evident as a prominent reduction current tail at potentials more negative than −0.400 V. This, in conjunction with the adsorption and stabilizing influence of polyacrylic acid, facilitates exceptional analytical sensitivity for the detection of gaseous H 2 O 2. The sensor exhibits the capability to detect concentrations of gaseous H 2 O 2 as low as 10−11 mol L−1, accomplished through the utilization of square-wave voltammetry and other advanced voltammetric techniques. [ABSTRACT FROM AUTHOR]

Abstract: The electrochemical reduction of lactofen (LCT) at the glassy carbon (GCE) and silver amalgam film electrode (AMFE) is investigatedin detail by the means of square wave voltammetry (SWV), square wave stripping voltammetry (SWSV) and cyclic voltammetry. The influence of various factors such as supporting electrolyte composition and SW parameters were studied. The AMFE electrode showed an excellent electrochemical activity toward the electro‐reduction of LCT, leading to a significant improvement in sensitivity as compared to the glassy carbon electrode.The SWSV detection limits for GCE and AMFE were 285.0 nM and 2.0 nM, respectively. The applicability of the developed voltammetric method for analysis of tap water and river water is illustrated with spiked samples analysis. Moreover, as lactofen is highly toxic to fish and other aquatic organisms, its interaction with dsDNA isolated from salmon sperm was tested. The intercalative mode of LCT binding to dsDNA was estimated. The heterogeneous rate constants were calculated for the free LCT and the LCT‐dsDNA complex. Moreover, LCT‐dsDNA complex binding ratio and equilibrium constant were determined. The decrease in the SWV peak current of LCT in the presence of dsDNA was used for the determination of dsDNA. [ABSTRACT FROM AUTHOR]

For the purpose of simplification of the electrochemical study under conditions of square-wave voltammetry (SWV), a simplified form of potential modulation is proposed by replacing the staircase potential ramp with a constant potential. The resulting potential modulation, which could be considered as a pulse form of a chronoamperometric experiment (i. e., square-wave chronoamperometry), is provisionally termed as electrochemical faradaic spectroscopy, considering the fact that the main tool in the kinetic analysis is the frequency of the potential pulses applied. The proposed technique is illustrated with theoretical analysis of a simple, kinetically controlled electrode reaction of a dissolved redox couple and experimentally verified with the Eu3+(aq)/Eu2+(aq) redox couple at a mercury electrode. The square-wave chronoamperometry exhibits unique features of the response absent in both conventional SWV and chronoamperometry, widening the range of accessible electrode kinetics. [ABSTRACT FROM AUTHOR]

The electrochemical behaviour of profluralin (PFL) was investigated with square wave voltammetry (SWV) and cyclic voltammetry at bare and modified with graphene, graphene oxide, reduced graphene oxide, carbon nanotubes glassy carbon electrode. The influence of various factors such as pH, buffer composition, ionic surfactants and voltammetric parameters was studied. The best results in terms of signal shape and intensity were recorded in 0.04 M Britton-Robinson buffer at pH 2.0 at −0.43 V versus Ag/AgCl. In acidic medium profluralin produces single cathodic signal of an irreversible nature. Observed peak (two superimposed signals from two nitro groups) is a result of PFL reduction controlled by diffusion processes. Linearity of peak currents ( Ip) vs. concentrations of profluralin was found in the range of 1.0×10−7 to 1.0×10−6 M with a detection limit of 2.6×10−8 M using fast and sensitive SWV. The developed method has been applied for the quantitative analysis of profluralin in spiked environmental samples with very good average recoveries in the range from 98.6 to 99.9 % with a mean relative standard deviation of 4.0 %. [ABSTRACT FROM AUTHOR]

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 Eu 3+ /Eu 2+ and azobenzene/hydrazobenzene redox couples. [ABSTRACT FROM AUTHOR]

The electrode kinetics of vitamin B2 was measured at a constant scan rate of a square-wave (SW) voltammetric experiment by recently introduced method based on alteration of the height (amplitude) of the SW potential pulses. The electrode reaction mechanism was analyzed in the light of the simplified model considering two-electron one step surface electrode mechanism, as well as to more appropriate EE surface reaction pathway consisting of two successive one-electron quasireversible reactions. Theoretical analysis indicated that the evolution of the voltammetric response under variation of the SW amplitude enables estimation of the rate determining step of the EE mechanism. [ABSTRACT FROM AUTHOR]

A novel methodological approach for processing electrochemical data measured under conditions of square-wave voltammetry (SWV) is proposed. The methodology takes advantage of the chronoamperometric characteristics of the electrochemical system observed in the course of the voltammetric experiment, which are commonly not considered in conventional SWV. The method requires processing of a single voltammogram only, measured under given set of the potential modulation parameters (i.e. SW frequency and height of the potential pulses). The core idea is to analyze the variation of the current with time, considering the last quarter time period of each potential pulse of the potential modulation, instead of measuring the single current value from the very end of the pulses. Hence, a single point current measurement is replaced with a multisampling current procedure, leading to a series of new SW voltammograms measured at different time increments of each potential pulse. The novel method is illustrated by the theoretical analysis of a quasireversible electrode reaction of a dissolved and surface confined redox couple, as well as a reversible electrode reaction preceded by a chemical equilibrium reaction (CrEr mechanism). [ABSTRACT FROM AUTHOR]

The kinetics of surface confined electrode reactions of alizarin, vitamin B12, and vitamin K2 is measured with square-wave voltammetry over a wide pH interval, by applying the recent methodology for kinetic analysis at a constant scan rate [V. Mirceski, D. Guziejewski, K. Lisichkov, Electrochim. Acta­ 2013, 114, 667-673]. The reliability and the simplicity of the recent methodology is confirmed. The methodology requires analysis of the peak potential separation of the forward and backward component of the response as a function of the pulse height (SW amplitude), for a given frequency (i.e. constant scan rate) of the potential modulation. [ABSTRACT FROM AUTHOR]

Abstract: A simple methodology for kinetic measurements of electrode processes is proposed under conditions of square-wave voltammetry (swv) at a constant scan rate of the voltammetric experiment. The method requires measurement of the peak potential separation between the forward and backward components of the voltammetric response by varying the sw amplitude, i.e., the height of the potential pulses. The methodology is equally valid for electrode reactions of an immobilized and dissolved redox couple. The estimation of the standard rate constant can be carried out either by direct fitting between the simulated and experimentally measured data, or by using the working curves derived by simulations. The proposed methodology was confirmed by kinetic measurements of the electrode reactions of azobenzene, immobilized on mercury electrode, and dissolved hexacyanoferrate at glassy carbon electrode. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

This article presents the theoretical prediction of square-wave amplitude effect on electrode reaction mechanisms coupled with chemical reaction under conditions of square-wave voltammetry. A systematic change in simulated voltammograms occurs following a change in the applied square-wave amplitude parameter. The obtained results help to assess the generated impact on the peak potential separation of square-wave forward and backward components from conventional and potential corrected voltammograms as well as on the so-called 'amplitude-based quasireversible maximum' acquired during the analysis of the net response peak height. In most cases, these features are independent of the parameters of coupled chemical reaction, and electrode kinetics can be estimated without their prior knowledge. Some characteristic criteria can be deduced from the observed trends, which can serve as a means to elucidate electron transfer kinetics. Under these conditions, even nonexperts in the square-wave voltammetry technique can characterize the studied experimental systems. Unlabelled Image • Analysis of mechanisms with coupled chemical reaction at a constant scan rate • Estimation of electrode reaction kinetics with SW amplitude effect only • Implementation of amplitude-based quasireversible maximum • Application of SW components separation size • Introduction of new features related to the electrode kinetics [ABSTRACT FROM AUTHOR]