Glassy Carbon Rotating Disk Electrode Research Articles

Effect of the ionic strength of the supporting electrolyte on the kinetics of albumin adsorption at a glassy carbon rotating disk electrode

The effect of the ionic strength of the supporting electrolyte (phosphate buffer, pH = 7.4, xM + 10 −2 x M Fe(CN) 6K 4, 25°C, 10 −2 ⩽ x ⩽ 1) on the kinetics of the adsorption of bovine serum albumin at a glassy carbon rotating disk electrode ( rde) was investigated. The kinetics were determined by analysing the double-layer capacitance C d( t) variation during adsorption. The experimental variation obeys the following relationship: C d( t) = a 0 + Σ i a i exp(− t/τ i ) the number i of detectable exponential functions depending on ionic strength. The time-constants τ i are related to the kinetic parameters of the successive irreversible steps of the mechanism, and a 0, a i to the double layer capacitance for the various states of the interface (bare or entirely covered by the adsorbed protein in state i). All the calculated parameters depend on the ionic strength. The various effects are explained by three modifications induced by the ionic strength change, ie (i) a change of the electrical charge of the interface, (ii) a change of the electrical charge of the protein and (iii) a change of the diffuse double-layer thickness.

Comparison of stripping methods at thin-film mercury electrodes

When a thin mercury film covered glassy carbon rotating disc electrode (TMFGCRDE) was used in square-wave anodic stripping voltammetric measurements, the highest sensitivity was obtained when the electrode was rotated slowly. The application of advanced analytical instrumentation to such measurements requires the addition of mercury ions to the sample.

Electro‐Oxidation of Formaldehyde on Thermally Prepared RuO2 and Other Noble Metal Oxides

The electro‐oxidation of formaldehyde has been investigated at thermally prepared noble metal oxides, especially, in aqueous solution. Studies were carried out on thin layers of oxide supported on Ta or Ti, and on thin, Teflonbonded oxide layers attached to a glassy carbon rotating disk electrode. The catalytic activity of for oxidation was considerably greater than that of and . At , formaldehyde was observed to undergo oxidation to formate at potentials from ca. 0.75–1.25V vs. reference hydrogen electrode (RHE), and to carbonate at higher potentials. The results suggest that (and ) oxidation is mediated by higher valent states of the oxide metal ions electrogenerated at the electrode surface. Values of 10−3 cm s−1 (geometric electrode area based) and 10−6 cm s−1 (real area based) were estimated for the heterogeneous rate constant for oxidation at . The activity for oxidation is correlated with the catalytic activity of the oxides for the oxygen gas evolution reaction.

A method for the efficient degradation of melphalan into nonmutagenic products

A new chemical method has been developed for the destruction of an antineoplastic agent melphalane in laboratory waste, based on its oxidation by potassium permanganate in sodium hydroxide medium. To monitor the efficiency of destruction, analytical methods based on UV spectrophotometry, differential pulse voltammetry on a glassy carbon rotating disk electrode, and HPLC coupled with UV spectrophotometry have been developed. It has been demonstrated that the proposed method of destruction is highly efficient (more than 99.8% destruction) and the corresponding degradation products were found to be nonmutagenic to Salmonella typhimurium strains TA98, TA100, and TA1535, in both the presence and the absence of a rat liver S9 activation system.

Determination of the kinetic parameters for the Ti(III)/Ti(IV) couple using a rotating disk electrode

The rate constant k° and the charge-transfer coefficient α for the oxidation—reduction system Ti(III)/Ti(IV) have been determined at a glassy-carbon rotating disk electrode in 5 M hydrochloric acid. The carhge transfer coefficient for the reaction Ti(III) → Ti(IV) is found to be 0.18, which is in agreement with previous results, obtained in a different way, by other authors. The charge transfer coefficient for the Ti(IV) → Ti(III) reaction turns out to be 0.11, and to our knowledge was not obtained before.

Kinetics studies of oxidations of catechol and l-dopa as mediated by IrCl i2−6 at polymer-coated glassy carbon electrodes

Rotating disk techniques were employed to measure the kinetics of the oxidations of catechol and l-dopa as mediated by IrCl 2− 6 at a glassy carbon rotating disk electrode coated with a mixture of two polycationic electrolytes. For both reactants the kinetic behavior matched that described by Andrieux et al. [1] for an “SR” case. Products of the cross-reaction rate constants and substrate partition coefficients derived from the data had values consistent with very similar reactivities of both substrates toward IrCl 2− 6 inside and outside of the coatings.

Differential pulse anodic stripping voltammetry of cadmium(II) with a rotating membrane-covered mercury film electrode

A rotating membrane-covered mercury film electrode (MCMFE) was constructed by placing a dialysis membrane over a glassy carbon rotating disk electrode and plating a thin mercury film onto the electrode surface through the membrane. Differential pulse anodic stripping voltammetry of cadmium was used to evaluate the effects of pH, rotation rate, deposition time, and concentration on the MCMFE. The response was linear from 4.0 X 10/sup -9/ MCd/sup 2 +/ to 1.07 X 10/sup -5/ M Cd/sup 2 +/ with a standard deviation of +/- 9.30 X 10/sup -10/ M Cd/sup 2 +/ for a 1.78 X 10/sup -8/ M Cd/sup 2 +/ solution (RSD +/- 11.1%) and a standard deviation of +/- 6.44 X 10/sup -9/ M Cd/sup 2 +/ for a 1.78 X 10/sup -/' M Cd/sup 2 +/ solution (RSD +/- 3.64%). The limit of detection was estimated to be 8.6 X 10/sup -10/ M. These results compared favorably to the bare mercury film electrode (MFE) for linear scan anodic stripping voltammetry. 29 references, 5 figures.

The electrocatalytic influence of underpotential lead adsorbates on the reduction of oxygen at glassy carbon electrodes in acid solution

The electrochemical reduction of oxygen and hydrogen peroxide has been investigated on a glassy carbon rotating disk electrode in 0.5 M HClO 4 at various concentrations of Pb 2+. An overall 2-electron reduction of O 2 to H 2O 2 is found on glassy carbon which, in the presence of Pb 2+, is positively catalyzed. The electrocatalytic effect can be correlated to an underpotential deposition (UPD) of lead at a limited number of active sites on the glassy carbon surface. The hydrogen peroxide reduction is nearly completely inhibited by the UPD of lead. The observed concentration dependence with respect to Pb 2+ is in accordance with the Nernstian behaviour of the UPD process.

Electrochemical study of d-glucose oxidase autoinactivation

The immobilization of a d-glucose oxidase (β- d-glucose: oxygen 1-oxidoreductase, EC 1.1.3.4) monolayer onto a glassy carbon rotating disc electrode allows the measurement of concentrations in the enzyme's microenvironment and, hence, gives a method of easily following its activity. As it functions, d-glucose oxidase undergoes an autoinactivation which is clearly distinct from inactivation by H 2O 2, and which is more severe as the concentration of the two substrates is increased. It appears that the number of catalytic cycles is fixed at 10 7, irrespective of the concentrations of the two substrates. Kinetically, it is the enzyme-substrate complex which seems to be inactivated. Scavengers of toxic species of O 2 have no effect on the kinetics of autoinactivation. Identical results were found in solution.

Electrochemical study of the oxidation of tin(II) at glassy carbon electrodes

The voltammetric characteristics of the Sn(IV)/Sn(II) system have been studied at a glassy carbon rotating disk electrode in 4 M hydrochloric acid. Anodic oxidation of Sn(II) produces a single well-defined wave, which has been examined in the temperature range 20–50°, and shows distinct irreversibility. The kinetic parameters of the oxidation reaction have been calculated. Kinetic features of the reduction of Sn(IV) to Sn(II) were not evaluated because the reduction proceeds directly to tin metal.

Electrochemical study of the Sb(V)/Sb(III) couple on a glassy carbon rotating-disk electrode

The kinetics of the reduction of Sb(V) at a glassy carbon rotating-disk electrode have been investigated in 9.5 M HCl. The current-potential curve is characterized by a single irreversible wave, the limiting current being linearly related to the Sb(V) concentration and the square root of the rotation rate. Kinetic parameters of the reaction have been evaluated. Anodic oxidation currents of Sb(III) cannot be quantitatively measured owing to the interference of the oxidation of chloride.

Electrochemical study of the Sb(V)/Sb(III) couple on a glassy carbon rotating-disk electrode

The kinetics of the reduction of Sb(V) at a glassy carbon rotating-disk electrode have been investigated in 9.5 M HCl. The current-potential curve is characterized by a single irreversible wave, the limiting current being linearly related to the Sb(V) concentration and the square root of the rotation rate. Kinetic parameters of the reaction have been evaluated. Anodic oxidation currents of Sb(III) cannot be quantitatively measured owing to the interference of the oxidation of chloride.

An Electrochemical Study of Chromium in Molten NaCl ‐ AlCl3

Chromium, introduced into melt as, underwent two reduction steps at a glassy carbon disk electrode. For the first reduction wave, and vs. a reference electrode of aluminum in at 175°C. The stationary electrode voltammetric response indicated that a reversible chemical step preceded electron transfer. A second reduction wave, ca. 0.1–0.2V, was attributed to the deposition of . The chronoamperometric response for this wave was similar in form to that observed for nucleation rate‐controlled depositions. Reoxidation of the deposit on the surface of a glassy carbon rotating disk electrode indicated that the oxidation product of this deposit, most likely a Cr(II) species, was adsorbed on the electrode surface. The adsorption of this species could be eliminated by employing either increased scan rates or higher temperatures. No chromium species other than Cr(III), Cr(II), and could be generated within the anodic limit of the melt, viz., 2.2V, in the temperature range of this study.

Determination of some metals and their mixtures by stripping chronopotentiometry on a glassy carbon rotating disk electrode

Determination of some metals and their mixtures by stripping chronopotentiometry on a glassy carbon rotating disk electrode

The deposition and stripping of mercury on a glassy carbon rotating disk electrode

The deposition and stripping of mercury on a glassy carbon rotating disk electrode

The deposition and stripping of mercury on a glassy carbon rotating disk electrode

Summary The deposition and stripping behaviour of mercury on a rotating glassy carbon disk electrode has been studied in nitric acid, thiocyanate and ammonium chloride media. It was found that the deposition occurs at sites of varying activity, and that deposition of larger amounts leads to formation of mercury droplets, the size and distribution of which depends on the deposition potential. The adsorption-desorption behaviour of ionic and molecularly complexed mercury is also discussed.

Voltammetry with disk electrodes and its analytical application VIII. The cyclic voltammetry of copper(II) at the glassy carbon rotating disk electrode

The cyclic voltammetry of copper(II) at the glassy carbon rotating disk electrode has been studied in a number of media with a view to its usefulness in analytical applications. It has been found that, while Cu2+ is generally reduced to Cu0, the stripping scan does not necessarily result in reoxidation to Cu2+, the reaction often ending with oxidation of Cu0 to monovalent copper. This phenomenon has been related to the degree to which monovalent copper, produced at the electrode surface, remains adsorbed long enough to undergo further reaction, which is, in turn, strongly affected by the medium.

Voltammetry with disk electrodes and its analytical application: VIII. The cyclic voltammetry of copper(II) at the glassy carbon rotating disk electrode

Summary The cyclic voltammetry of copper(II) at the glassy carbon rotating disk electrode has been studied in a number of media with a view to its usefulness in analytical applications. It has been found that, while Cu 2+ is generally reduced to Cu 0 , the stripping scan does not necessarily result in reoxidation to Cu 2+ , the reaction often ending with oxidation of Cu 0 to monovalent copper. This phenomenon has been related to the degree to which monovalent copper, produced at the electrode surface, remains adsorbed long enough to undergo further reaction, which is, in turn, strongly affected by the medium.

Voltammetry with disk electrodes and its analytical application V. The voltammetry of iron(III) at the glassy carbon rotating disk electrode in complexing media

Summary A study has been made of the suitability of glassy carbon as a rotating disk electrode for analytical use in acid media. The results are compared with those available in the literature for the voltammetric behaviour of iron(III) at other solid electrodes. The effects of temperature, electrode rotation rate, and potential scan speed on the reduction wave in acid media are followed and heterogeneous rate constants calculated by three methods. The charge transfer coefficient is found. Analytical determination limits are noted and the stability of the diffusion current over five minutes recorded. The reaction proceeds at least as favourably on glassy carbon as on other electrode materials, the disadvantages of an irreproducible electrode surface being avoided.

Voltammetry with disk electrodes and its analytical application V. The voltammetry of iron(III) at the glassy carbon rotating disk electrode in complexing media

Voltammetry with disk electrodes and its analytical application V. The voltammetry of iron(III) at the glassy carbon rotating disk electrode in complexing media