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A number of experimental approaches that should offer improved S/N in electrochemical detection were evaluated and compared. In addition, to evaluate and optimize the electrochemical response behavior of analytes under actual CE conditions, an on-line cyclic voltammetry (CV) system was developed. The experimental parameters examined included waveform shape, waveform frequency and various signal treatments, using a lock-in amplifier and Fourier analysis. A multiple-step pulse waveform provided the maximum S/N enhancement [up to 10-fold relative to pulse amperometric detection (PAD)], with detection limits in the range of 2·10−8 to 2·10−7 mol/l. The use of the second harmonic from Fourier analysis offered the best improvement in baseline stability. Other approaches such as high pulse frequency (100 to 200 Hz), data collection over selected time windows, digital filters and average smoothing also enhanced S/N 2- to 5-fold relative to PAD. On-line CV studies showed that the adsorption of organic electrolytes on electrode surfaces can inhibit O2 reactions, and thus give low and stable background currents without O2 removal. The CV studies also showed that detection of Pb2+, Cu2+ and Ag+ affected subsequent electrode response, and that H+ evolution contributed to the cathodic signals of the analytes Ni2+, Co2+ and Zn2+.

Ammonium amalgam formation has been studied at mercury ultramicroelectrodes in various organic solvents and at standard size mercury electrodes in aqueous solution. Numerical simulations were carried out in order to establish the kinetics of the process. Ammonium amalgam is formed via a fast charge-transfer process, but it undergoes a decomposition according to the first-order rate law with a rate constant of about 0.6 s−1. In addition, some NH4+ ions are irreversibly discharged at the electrode surface, presumably to form H2 and NH3. This competing process is affected strongly by the nature of the solvent. Matching of experimental and simulated curves suggests that the diffusion coefficient of NH4 in mercury is about 1.8 × 10−5 cm2 s−1. The standard potential of NH4+(aq)/NH4(Hg) was determined to be −1.723 V/SHE. The absolute chemical potential of ammonium ions in mercury was calculated and compared with that of alkali metal ions.

The methodology for carrying out ac voitammetric measurements with ultramicroelectrodes is discussed. Electron-transfer rate constants for the oxidation of ferrocene (FeCp2) at a Pt ultramicroelectrode and cobaltocene (CoCp2) at Hg, Au and Pt ultramicroelectrodes were measured at frequencies from 2 to 50 kHz. It was shown that the method can provide accurate information about fast interfacial charge-transfer kinetics in organic solvents. The rate of CoCp2 oxidation on Hg or Au electrodes was found to increase with a decrease in the supporting electrolyte concentration, but in the case of the Pt electrode no effect of the supporting electrolyte concentration was observed for oxidation of either CoCp2 or FeCp2. The state of the Pt—solution interface was examined by studying the H+ adsorption—desorption process in aqueous H2SO4 and the double-layer capacitance in nonaqueous media.

Electrodeposition of alkali metals on Hg/Au electrodes from non-aqueous solutions was studied using cyclic voltammetry and chronoamperometry. At temperatures of 20 to − 70°C the formation of bulk intermetallic compounds preceded by nucleation phenomena was observed. Stoichiometry of the solid phases formed under these conditions was determined. At very low temperatures, when the mobility of mercury atoms was restricted, the underpotential deposition of alkali metal ions on solid mercury electrodes was noted. The Gibbs energies of electrosorption are discussed in terms of interactions between alkali metals and mercury.

Electrode processes involving the formation of a heterogeneous amalgam of iron during the electroreduction of Fe(II) ions on mercury and the oxidation of the iron amalgam were investigated by cyclic voltammetry, chronoamperometry and cyclic chronopotentiometry. The hanging mercury drop electrode and an iron plate placed on a mercury pool electrode were used in the experiments as working electrodes. It was established that particles of the electrodeposited iron are wetted by mercury and penetrate into the bulk of mercury electrodes forming a suspension. However, during electroreduction of Fe(II) ions from concentrated CaCl2 and Ca(ClO4)2 solutions a small amount of metallic iron remains on the surface of mercury. Oxidation of the heterogeneous amalgam of iron occurs at potentials about 100–150 mV less positive than the onset potential of mercury oxidation in the solutions studied. At these potentials oxidation of mercury may become significant enough to uncover some parts of the iron microcrystals. These iron particles become partially passivated and their surface energy at the Fe/solution interface decreases; consequently, the spreading coefficient of mercury on iron decreases, microcrystals of iron are expelled from mercury and finally oxidized.

The mechanism, of electrodeposition of CdS on Hg, and Pt electrodes has been studied in dimethylsulphoxide solutions by performing cyclic voltammetry at stationary electrodes and pulse polarography at dropping Hg electrodes in solutions containing both Cd(II) ions and elemental sulphur. Evidence is presented to demonstrate that sulphur is chemisorbed at these electrodes and that formation of at least a monolayer of metal sulphide is probable. As a result, formation of the initial layer of CdS involves reaction of Cd(II) ions with chemisorbed sulphur or with a pre-existing layer of metal sulphide. Data for the formation of CdS are compared with those obtained for the formation of PbS and ZnS.

Voltammetric data obtained at high sweep rates (> 10 kV/s) are usually distorted by the slow response of current transducers. An efficient correction of numerically acquired data can be accomplished by employing forward and inverse Fourier transform as well as the convolution transform. This method can be applied to any electrochemical experiment and it increases the effective bandwidth of current transducers by about one order of magnitude. An example of application in kinetic studies is given.

Polarographic half-wave potentials for two reduction steps of 49 cyclopentadienyliron complexes of substituted arenes or heterocycles in dimethylformamide were determined. A fast cyclic voltammetry (10–40 V/s) was used to study the electron transfer kinetics of some of these complexes. After correction for the double layer effects, the rate constants of all the complexes studied show that the transfer of electrons in the second reduction step occurs significantly faster than in the first one. This was interpreted as a result of greater delocalization of electrons in the 20-electron complexes of iron compared to the 19-electron complexes.

Polarographic half-wave potentials for two reduction steps of 49 cyclopentadienyliron complexes of substituted arenes or heterocycles in dimethylformamide were determined. A fast cyclic voltammetry (10–40 V/s) was used to study the electron transfer kinetics of some of these complexes. After correction for the double layer effects, the rate constants of all the complexes studied show that the transfer of electrons in the second reduction step occurs significantly faster than in the first one. This was interpreted as a result of greater delocalization of electrons in the 20-electron complexes of iron compared to the 19-electron complexes.