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Valentin Mirceski - One of the best experts on this subject based on the ideXlab platform.

  • new aspects of the electrochemical catalytic ec mechanism in Square Wave Voltammetry
    Electrochimica Acta, 2015
    Co-Authors: Rubin Gulaboski, Valentin Mirceski
    Abstract:

    Abstract Several new theoretical aspects of the electrocatalytic (regenerative) EC’ mechanism under conditions of Square-Wave (SWV) and staircase cyclic Voltammetry (SCV) are presented. Elaborating the effect of the rate of the catalytic reaction in the diffusion-controlled catalytic mechanism (diffusional EC’ mechanism) and surface catalytic mechanism (surface EC’ mechanism), we refer to several phenomena related to the shift of the position and the half-peak width of the net peak in Square-Wave Voltammetry (SWV). If the rate of the catalytic reaction is much higher than the kinetics of the electrode reaction, a linear dependence between the peak potential of the simulated net SWV peaks and the logarithm of the catalytic parameter can be observed. The intercept of that linear dependence is a function of the kinetics of the electrode reaction. Based on this finding, we propose a new methodology to determine the electrode kinetics rate constant. The proposed approach relies on the variation of the concentration of the regenerative reagent. To the best of our knowledge, this is one of very few voltammetric approaches for electrode kinetic measurements not based on the time or potential variation in the experimental analyzes. In addition, we present a brief analysis of the catalytic mechanism under conditions of staircase cyclic Voltammetry in order to emphasize the main differences between SCV and SWV.

  • RECENT ACHIEVEMENTS IN Square-Wave Voltammetry (A REVIEW)
    Macedonian Journal of Chemistry and Chemical Engineering, 2014
    Co-Authors: Valentin Mirceski, Rubin Gulaboski
    Abstract:

    Recent advances in Square-Wave Voltammetry for analytical purposes as well as for studying electrode mechanisms and kinetics are reviewed, mainly covering results published in the last decade. Analyzing only some typical analytically oriented studies, one confirms the well-known fact that the technique is attributed with superior analytical performance in the family of advance pulse voltammetric techniques. Covering all analytical studies where Square-Wave Voltammetry is the working technique is hardly possible. For this reason, we decided to cover the relevant studies in Square-Wave Voltammetry, mainly published in the last five to seven years. The reviewed period is marked with remarkable contributions in the theory of complex electrode mechanisms, revealing that Square-Wave Voltammetry is one of the most powerful voltammetric techniques for both mechanistic and kinetic characterizations of electrode processes. Finally, a brief consideration is given to several methodologically oriented studies, referring mainly to cyclic-Square Voltammetry as well as methods based on the analysis of electrode processes by varying the amplitude of the potential modulation, which is expected to expand the scope and application of the technique in coming years.

  • electrode kinetic measurements with Square Wave Voltammetry at a constant scan rate
    Electrochimica Acta, 2013
    Co-Authors: Valentin Mirceski, Dariusz Guziejewski, Kiril Lisichkov
    Abstract:

    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.

  • Square Wave Voltammetry a review on the recent progress
    Electroanalysis, 2013
    Co-Authors: Valentin Mirceski, Rubin Gulaboski, Milivoj Lovric, Ivan Bogeski, Reinhard Kappl, Markus Hoth
    Abstract:

    A review on the recent progress of Square-Wave Voltammetry is presented, covering the period of the last five years. The review addresses the new theoretical development of the technique as well as its application for mechanistic purposes, electrode kinetic measurements, biochemical and analytical applications. Besides, a few novel methodological modifications are proposed that might expand the scope and application of the technique.

  • new approach to electrode kinetic measurements in Square Wave Voltammetry amplitude based quasireversible maximum
    Analytical Chemistry, 2013
    Co-Authors: Valentin Mirceski, Eduardo Laborda, Dariusz Guziejewski, Richard G. Compton
    Abstract:

    The influence of the potential pulse height of Square-Wave Voltammetry (SWV) (i.e., the SW amplitude) is studied for a variety of quasireversible electrode mechanisms, including a simple solution-phase electrode reaction at a planar or spherical electrode, a solution phase electrode reaction coupled with a reversible follow-up chemical reaction, and a diffusionless surface confined electrode reaction. The electrode kinetics of all the electrode mechanisms depends critically on the SW amplitude, and the quasireversible kinetic region is a function of both frequency-related electrode kinetic parameters and the SW amplitude. Thus, a novel methodology for electrode kinetics measurements is proposed by altering the SW amplitude only, at a fixed frequency of the SW potential modulation, that is, at a constant scan rate of the voltammetric experiment. Electrode kinetic measurements at a constant SW frequency are of exceptional importance especially when complex electrode mechanisms are studied, which depend on s...

Richard G. Compton - One of the best experts on this subject based on the ideXlab platform.

  • electrochemical hg2 detection at tannic acid gold nanoparticle modified electrodes by Square Wave Voltammetry
    Analyst, 2018
    Co-Authors: Alex L Suherman, Sabine Kuss, Eden E L Tanner, Neil P Young, Richard G. Compton
    Abstract:

    We report the electrochemical sensing of Hg2+ based on tannic acid capped gold nanoparticle (AuNP@TA) complexes. At optimal conditions using Square Wave Voltammetry, the presented analytical method exhibits a “measurable lower limit” of 100.0 fM. This limit is considerably below the permissible level of 30.0 nM for inorganic mercury in drinking water, specified by the World Health Organization (WHO). The effect of potentially interfering ions, such as Zn2+ and Al3+, was studied and results indicate an excellent selectivity for Hg2+. The transfer of the proposed strategy onto AuNP@TA modified screen-printed electrodes demonstrates its applicability to routine monitoring of Hg2+ in tap water.

  • new approach to electrode kinetic measurements in Square Wave Voltammetry amplitude based quasireversible maximum
    Analytical Chemistry, 2013
    Co-Authors: Valentin Mirceski, Eduardo Laborda, Dariusz Guziejewski, Richard G. Compton
    Abstract:

    The influence of the potential pulse height of Square-Wave Voltammetry (SWV) (i.e., the SW amplitude) is studied for a variety of quasireversible electrode mechanisms, including a simple solution-phase electrode reaction at a planar or spherical electrode, a solution phase electrode reaction coupled with a reversible follow-up chemical reaction, and a diffusionless surface confined electrode reaction. The electrode kinetics of all the electrode mechanisms depends critically on the SW amplitude, and the quasireversible kinetic region is a function of both frequency-related electrode kinetic parameters and the SW amplitude. Thus, a novel methodology for electrode kinetics measurements is proposed by altering the SW amplitude only, at a fixed frequency of the SW potential modulation, that is, at a constant scan rate of the voltammetric experiment. Electrode kinetic measurements at a constant SW frequency are of exceptional importance especially when complex electrode mechanisms are studied, which depend on s...

  • new approach to electrode kinetic measurements in Square Wave Voltammetry amplitude based quasireversible maximum
    Analytical Chemistry, 2013
    Co-Authors: Valentin Mirceski, Eduardo Laborda, Dariusz Guziejewski, Richard G. Compton
    Abstract:

    The influence of the potential pulse height of Square-Wave Voltammetry (SWV) (i.e., the SW amplitude) is studied for a variety of quasireversible electrode mechanisms, including a simple solution-phase electrode reaction at a planar or spherical electrode, a solution phase electrode reaction coupled with a reversible follow-up chemical reaction, and a diffusionless surface confined electrode reaction. The electrode kinetics of all the electrode mechanisms depends critically on the SW amplitude, and the quasireversible kinetic region is a function of both frequency-related electrode kinetic parameters and the SW amplitude. Thus, a novel methodology for electrode kinetics measurements is proposed by altering the SW amplitude only, at a fixed frequency of the SW potential modulation, that is, at a constant scan rate of the voltammetric experiment. Electrode kinetic measurements at a constant SW frequency are of exceptional importance especially when complex electrode mechanisms are studied, which depend on several frequency-related kinetic parameters. The electrode kinetic measurements are based on a novel feature termed the "amplitude-based quasireversible maximum", manifested as a parabolic dependence of the amplitude-normalized net SW peak current versus the SW amplitude. The position of the amplitude-based quasireversible maximum depends on the standard rate constant of the electrode reaction, enabling estimation of this important kinetic parameter in a simple and fast procedure. The novel quasireversible maximum is attributed to all studied electrode mechanisms, implying that it is a general feature of most electrode mechanisms under conditions of SWV.

  • mass transport at electrodes of arbitrary geometry reversible charge transfer reactions in Square Wave Voltammetry
    Russian Journal of Electrochemistry, 2012
    Co-Authors: Angela Molina, Joaquín González, Eduardo Laborda, Richard G. Compton
    Abstract:

    The basis for mass transport of the electroactive species in different diffusion fields is examined, pointing out important insights in relation to the value of the surface concentrations for the case of fast electrode processes. Moreover, a general analytical solution for the transient current is given for several geometries, when an arbitrary sequence of potentials pulses is applied to macroelectrodes (planar), spheres, cylinders, discs and bands. The results are particularized for Square Wave Voltammetry. Explicit solutions for the net current and the forward and backward components are given. The effects of frequency, pulse amplitude and electrode size or shape on the peak current are studied. Moreover, the conditions for the attainment of the steady state response are analyzed in the different geometries as well as the characteristics of this response.

  • Square Wave Voltammetry at disc microelectrodes for characterization of two electron redox processes
    Physical Chemistry Chemical Physics, 2012
    Co-Authors: Angela Molina, Eduardo Laborda, Christopher Batchelormcauley, Richard G. Compton
    Abstract:

    Analytical explicit solutions are presented for the use of Square Wave Voltammetry (SWV) at disc microelectrodes to study two-electron reversible redox processes. This combines the advantages of SWV (minimization of capacitative effects, peak-shaped response and quick experiments) with those of microelectrodes (reduction of capacitative and ohmic drop effects, enhanced mass transport and measurements of small volumes). Further, the analytical expressions are very easy to implement in comparison with the numerical methods usually employed for simulation of electrochemical experiments at microdisc electrodes. From the theory, the effects of the technique parameters (frequency, pulse amplitude) are examined and procedures are given for the characterization of the redox system from the values of the peak current, peak potential and half-peak width. Finally, the theory is applied to the experimental study of the two-electron reduction of anthraquinone-2-sulfonate in aqueous media. For this system, the formal potentials of the redox centres in aqueous solutions can be tuned by means of the electrolyte cation.

Milivoj Lovric - One of the best experts on this subject based on the ideXlab platform.

  • Square Wave Voltammetry a review on the recent progress
    Electroanalysis, 2013
    Co-Authors: Valentin Mirceski, Rubin Gulaboski, Milivoj Lovric, Ivan Bogeski, Reinhard Kappl, Markus Hoth
    Abstract:

    A review on the recent progress of Square-Wave Voltammetry is presented, covering the period of the last five years. The review addresses the new theoretical development of the technique as well as its application for mechanistic purposes, electrode kinetic measurements, biochemical and analytical applications. Besides, a few novel methodological modifications are proposed that might expand the scope and application of the technique.

  • Square Wave Voltammetry
    2007
    Co-Authors: Milivoj Lovric
    Abstract:

    Square-Wave Voltammetry (SWV) is one of the four major voltammetric techniques provided by modern computer-controlled electroanalytical instruments, such as Autolab and μAutolab (both EcoChemie, Utrecht), BAS 100 A (Bioanalytical Systems), and PAR Model 384 B (Princeton Applied Research) [1]. The other three important techniques are single scan and cyclic staircase, pulse, and differential pulse Voltammetry (see Chap. II.2). All four are either directly applied or after a preconcentration to record the stripping process. The application of SWV boomed in the last decade, first because of the widespread use of the instruments mentioned above, second because of a well-developed theory, and finally, and most importantly, because of its high sensitivity to surface-confined electrode reactions. Adsorptive stripping SWV is the best electroanalytical method for the determination of electroactive organic molecules that are adsorbed on the electrode surface [2].

  • ohmic drop effects in Square Wave Voltammetry
    Journal of Electroanalytical Chemistry, 2001
    Co-Authors: Valentin Mirceski, Milivoj Lovric
    Abstract:

    The ohmic drop effects in Square-Wave Voltammetry (SWV) are studied theoretically. Three different electrode mechanisms are considered: (i) simple redox reaction of a dissolved redox couple, (ii) redox reaction with adsorption of the reactant and (iii) surface redox reaction of a strongly immobilized redox couple. The ohmic drop effect is represented through the complex dimensionless resistance parameter defined as ρ=(nF)2S(cOx)0(Df)1/2RΩ(RT)−1 for (i) and (ii) and ρs=(nF)2SΓ0RΩf(RT)−1 for (iii). The relationships between the properties of the SWV response and the resistance parameters are investigated thoroughly. An attempt is made to establish criteria for distinguishing the kinetic from the ohmic drop phenomena. The influence of the ohmic drop on the quasi-reversible maximum in the case of adsorption-complicated redox reactions (ii) and (iii) is analyzed. The error that can be involved in the estimation of the standard rate constant using the quasi-reversible maximum in the presence of ohmic drop is evaluated in the case of the surface redox reaction (iii).

  • Square Wave Voltammetry of a cathodic stripping reaction complicated by adsorption of the reacting ligand
    Analytica Chimica Acta, 1999
    Co-Authors: Valentin Mirceski, Milivoj Lovric
    Abstract:

    Abstract 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 1 mol dm −3 KNO 3 are estimated as follows: standard rate constant k s =25±5 s −1 and cathodic transfer coefficient α =0.6±0.1. The adsorption constant of 6-propyl-2-thiouracil on the mercury surface in 1 mol dm −3 KNO 3 is estimated to be in the range: 0.1≤log( K /cm −1 )≤1.2.

  • a cathodic stripping Square Wave Voltammetry of a second order redox reaction and its application to the mercury cysteine system
    Electroanalysis, 1998
    Co-Authors: Valentin Mirceski, Milivoj Lovric
    Abstract:

    A model of cathodic stripping Square-Wave Voltammetry of a second-order redox reaction is developed. Both reversible and quasireversible redox reactions are considered. The relationships between the properties of SWV response and both parameters of the redox reaction and the SWV excitation signal are analyzed. The effect of the concentration of the reacting ligand on the SW voltammograms is discussed. The phenomenon of a quasireversible maximum is demonstrated. Numerical simulations are compared qualitatively with the cathodic stripping Square-Wave voltammetric response of cysteine.

A Chtaini - One of the best experts on this subject based on the ideXlab platform.

  • electrochemical determination of cadmium ii at platinum electrode modified with kaolin by Square Wave Voltammetry
    Journal of Hazardous Materials, 2009
    Co-Authors: M El A Mhammedi, M Achak, M Hbid, M Bakasse, T Hbid, A Chtaini
    Abstract:

    In this work, determination of cadmium(II) using Square Wave Voltammetry (SWV) was described. The method is based on accumulation of these metal ions on kaolin platinum electrode (K/Pt). The K/Pt performance was optimized with respect to the surface modification and operating conditions. The optimized conditions were obtained in pH of 5.0 and accumulation time of 25 min. Under the optimal conditions, the relationship between the peak current versus concentration was linear over the range of 9 x 10(-8) to 8.3 x 10(-6) mol L(-1). The detection limit (DL, 3sigma) was 5.4 x 10(-9) mol L(-1). The analytical methodology was successfully applied to monitor the Cd(II) content in natural water. Interferences were also evaluated.

  • ca10 po4 6 oh 2 modified carbon paste electrode for the determination of trace lead ii by Square Wave Voltammetry
    Journal of Hazardous Materials, 2009
    Co-Authors: M El A Mhammedi, M Achak, A Chtaini
    Abstract:

    Abstract The analytical performance of hydroxyapatite Ca 10 (PO 4 ) 6 (OH) 2 (HAp) screen-printed sensors designed for the detection of metals was evaluated. The hydroxyapatite plays an important role in modern analytical electrochemistry due to their usefulness for the preparation of sensors giving rise to improved responses from metals. The suitable HAp-modified carbon-paste electrode (HAp-CPE) for the electrochemical determination of lead is illustrated in this work using cyclic and Square-Wave Voltammetry in the potential range between −0.3 and −0.8 V. Perchlorate acid solution (1.0 mol L −1 ) was employed as the supporting electrolyte. The voltammetric measurements were carried out using as working electrode HAp-CPE, and a platinum electrode and an SCE electrode as auxiliary and reference electrodes, respectively. Under the optimized working conditions, calibration graph is linear for 5 min of preconcentration time with the detection limit 7.68 × 10 −10  mol L −1 . This detection limit is remarkably lower than those reported previously using other modified electrodes or amperometric detection. The results indicate that this electrode is sensitive and effective for the determination of Pb 2+ .

  • electrochemical studies and Square Wave Voltammetry of paraquat at natural phosphate modified carbon paste electrode
    Journal of Hazardous Materials, 2007
    Co-Authors: M El A Mhammedi, M Bakasse, A Chtaini
    Abstract:

    A Square Wave Voltammetry (SWV) method for the determination of trace amounts of paraquat at carbon paste electrode modified with natural phosphate (NP-CPE) is proposed. Paraquat was accumulated onto natural phosphate at open circuit potential from aqueous solution. The reduction peaks of paraquat were observed around -0.7V and -1.0V (versus SCE). The response of paraquat at NP-CPE related to: the concentration of this herbicide, preconcentration time, natural phosphate loading and measuring solution pH, was investigated. It was observed that the increase of the cathodic peak currents using SWV, under the optimized condition, is linear with the increase of paraquat concentration in the range from 2.3x10(-8)molL(-1) to 300x10(-8)molL(-1). The detection limit (DL, 3S.D.) and quantification limit (QL, 10S.D.) for peak 1 were about 7.8x10(-10)molL(-1) and 2.59x10(-9)molL(-1), respectively, in pure electrolyte water with the relative standard deviation of 1.8% (n=7). The proposed method was successfully applied to the determination of paraquat in real water samples with satisfactory results.

Eduardo Laborda - One of the best experts on this subject based on the ideXlab platform.

  • new approach to electrode kinetic measurements in Square Wave Voltammetry amplitude based quasireversible maximum
    Analytical Chemistry, 2013
    Co-Authors: Valentin Mirceski, Eduardo Laborda, Dariusz Guziejewski, Richard G. Compton
    Abstract:

    The influence of the potential pulse height of Square-Wave Voltammetry (SWV) (i.e., the SW amplitude) is studied for a variety of quasireversible electrode mechanisms, including a simple solution-phase electrode reaction at a planar or spherical electrode, a solution phase electrode reaction coupled with a reversible follow-up chemical reaction, and a diffusionless surface confined electrode reaction. The electrode kinetics of all the electrode mechanisms depends critically on the SW amplitude, and the quasireversible kinetic region is a function of both frequency-related electrode kinetic parameters and the SW amplitude. Thus, a novel methodology for electrode kinetics measurements is proposed by altering the SW amplitude only, at a fixed frequency of the SW potential modulation, that is, at a constant scan rate of the voltammetric experiment. Electrode kinetic measurements at a constant SW frequency are of exceptional importance especially when complex electrode mechanisms are studied, which depend on several frequency-related kinetic parameters. The electrode kinetic measurements are based on a novel feature termed the "amplitude-based quasireversible maximum", manifested as a parabolic dependence of the amplitude-normalized net SW peak current versus the SW amplitude. The position of the amplitude-based quasireversible maximum depends on the standard rate constant of the electrode reaction, enabling estimation of this important kinetic parameter in a simple and fast procedure. The novel quasireversible maximum is attributed to all studied electrode mechanisms, implying that it is a general feature of most electrode mechanisms under conditions of SWV.

  • new approach to electrode kinetic measurements in Square Wave Voltammetry amplitude based quasireversible maximum
    Analytical Chemistry, 2013
    Co-Authors: Valentin Mirceski, Eduardo Laborda, Dariusz Guziejewski, Richard G. Compton
    Abstract:

    The influence of the potential pulse height of Square-Wave Voltammetry (SWV) (i.e., the SW amplitude) is studied for a variety of quasireversible electrode mechanisms, including a simple solution-phase electrode reaction at a planar or spherical electrode, a solution phase electrode reaction coupled with a reversible follow-up chemical reaction, and a diffusionless surface confined electrode reaction. The electrode kinetics of all the electrode mechanisms depends critically on the SW amplitude, and the quasireversible kinetic region is a function of both frequency-related electrode kinetic parameters and the SW amplitude. Thus, a novel methodology for electrode kinetics measurements is proposed by altering the SW amplitude only, at a fixed frequency of the SW potential modulation, that is, at a constant scan rate of the voltammetric experiment. Electrode kinetic measurements at a constant SW frequency are of exceptional importance especially when complex electrode mechanisms are studied, which depend on s...

  • mass transport at electrodes of arbitrary geometry reversible charge transfer reactions in Square Wave Voltammetry
    Russian Journal of Electrochemistry, 2012
    Co-Authors: Angela Molina, Joaquín González, Eduardo Laborda, Richard G. Compton
    Abstract:

    The basis for mass transport of the electroactive species in different diffusion fields is examined, pointing out important insights in relation to the value of the surface concentrations for the case of fast electrode processes. Moreover, a general analytical solution for the transient current is given for several geometries, when an arbitrary sequence of potentials pulses is applied to macroelectrodes (planar), spheres, cylinders, discs and bands. The results are particularized for Square Wave Voltammetry. Explicit solutions for the net current and the forward and backward components are given. The effects of frequency, pulse amplitude and electrode size or shape on the peak current are studied. Moreover, the conditions for the attainment of the steady state response are analyzed in the different geometries as well as the characteristics of this response.

  • Square Wave Voltammetry at disc microelectrodes for characterization of two electron redox processes
    Physical Chemistry Chemical Physics, 2012
    Co-Authors: Angela Molina, Eduardo Laborda, Christopher Batchelormcauley, Richard G. Compton
    Abstract:

    Analytical explicit solutions are presented for the use of Square Wave Voltammetry (SWV) at disc microelectrodes to study two-electron reversible redox processes. This combines the advantages of SWV (minimization of capacitative effects, peak-shaped response and quick experiments) with those of microelectrodes (reduction of capacitative and ohmic drop effects, enhanced mass transport and measurements of small volumes). Further, the analytical expressions are very easy to implement in comparison with the numerical methods usually employed for simulation of electrochemical experiments at microdisc electrodes. From the theory, the effects of the technique parameters (frequency, pulse amplitude) are examined and procedures are given for the characterization of the redox system from the values of the peak current, peak potential and half-peak width. Finally, the theory is applied to the experimental study of the two-electron reduction of anthraquinone-2-sulfonate in aqueous media. For this system, the formal potentials of the redox centres in aqueous solutions can be tuned by means of the electrolyte cation.

  • electrochemical oxidation of nitrite kinetic mechanistic and analytical study by Square Wave Voltammetry
    Journal of Electroanalytical Chemistry, 2012
    Co-Authors: Ying Wang, Eduardo Laborda, Richard G. Compton
    Abstract:

    Abstract The voltammetric determination of nitrite is in principle a very competitive method by virtue of being fast, easy to apply, economical and portable. In order to optimize the experimental conditions for the analytical determination it is essential to understand the reaction scheme and kinetics of the redox system. With this purpose, in this paper Square Wave Voltammetry is employed to examine the electro-oxidation of nitrite. The reaction mechanism and electrode kinetics are investigated, pointing out the effects of the solution pH, the electrode material (glassy carbon, edge plane pyrolytic graphite and gold) and the supporting electrolyte. A second order catalytic mechanism justifies the experimental results, with the nitrite being regenerated by disproportionation of the electrogenerated NO2 with a rate constant kdisp = (2.0 ± 0.1) × 106 M−1 s−1. The electrode reaction is found to be reversible on gold macroelectrodes and much slower on carbon based electrodes with blocking effect due to the presence of perchlorate anions.