Portugaliae
Electrochimica Acta

Solutions of [CuL] (CI04)2, [CuLCI] (CI04), [CuLBr] (CI04), and [CuL(NCS)2], (L=Ci7H25N3S2; structure below) in acetonitrile give well-defined cyclic voltammograms with a gold disk as working electrode. One electron metal-centered, reversible or quasi-reversible oxidation-reduction processes were observed. Differences in the cyclovoltammetric behaviour of the four complexes correspond to differences in their structures. The half-wave potentials are not unusually high, and only that of [CuL] (CI04)2 falls within the range found for Typel copper proteins. These observations will be described and discussed.

Distributions of the induction times of silver potentiostatic electrodeposition coupled with hydrogen peroxide oxidation/reduction onto carbon microelectrodes have been obtained. The nucleation process has been shown to be affected by kinetic complexities due to the disproportionation of hydrogen peroxide and therefore neither the pure birth model nor the birth and death electronucleation model have shown to be applicable to this system. The double potential step and linear sweep voltammetry measurements point to the formation of silver peroxy species during the electrodeposition process.

The concept of ion pair and the way it has been presented in the literature is critically discussed.

The concepts of absolute and relative electrode potential and their relationship to the structure of the metal/electrolyte interface are presented. The necessity of distinguishing between electrode potential and electromotive force of a half-cell reaction, particularly in teaching, is highlighted. It is shown that electrode potential should be the concept recommended for defining the electrode interface potential drop.

In vitro studies were conducted to quantify the amount of iron species released from AISI 316L stainless steel biomaterial during its implantation either in human beings or animals. By constructing calibration curves for those species using the cyclic voltammetry technique it was possible to determine the iron ions levels in physiological medium.

The electro-oxidation of D-sorbitol in aqueous perchloric medium was used as a test of the electrocatalytic activity of platinum, platinum-indium and iridium electrodes. Cyclic voltammetry was the main technique used in this study. Results have shown almost no activity for Ir electrodes and similar activities for Pt and Pt-Ir. slightly higher for Pt-Ir (90:10) electrodes.

Conductance measurements of S-n-butylisothiouronium bromide, -iodide and -picrate (S-n-Buis Br, S-n-Buis I and S-n-Buis Pi) in methanol-nitrobenzene mixtures at approximately 0.25, 0.5 and 0.75 mole fractions of methanol were studied at 25 °C, 35 °C and 45°C respectively. The data were analyzed using Fuoss' equation0^ (1980) to derive the molar conductance at infmitesirnal concentration, A, the association distance R and the association constant KA corresponding to minimum standard deviation oA. The discussion was based on the variation of anionic size, the mole fraction of methanol and with varying temperature taking into account ionic solvation and viscosity effect. Thermodynamic parameters AG/(kJ/mole), AH/(kJ/mole) and AS/(J moi1 K1) were calculated and interpreted according to the variation of temperature and the mole fraction of methanol.

In the present study, the electrochemical oxidation of 5-hydroxytryptophol, a normal metabolite of the indol amines 5-hydroxytryptophan and 5-hydroxytryptamine was investigated using various electrodes in different electrolyte solutions. It was concluded that the electrooxidation mechanism depended on the electrolyte. pH, scan rate and the nature of the electrode.

Voltammetric studies revealed that under transient conditions in neutral pH gluconate solutions, the electroactive species are Sn(GH^) . The formation of monovalent species is slow. Gluconate prevents the formation of Sn(OH)^. In high alkali solutions, the adsorbed monovalent species obey to a non activated Temkin adsorption isotherm and the first electron transfer is slow. The gluconates interact with SniOH)^ and hinder the participation of OH ions in the deposition process.