Portugaliae
Electrochimica Acta

The transfer of electrons across the electrode-solution interface has long been the subject of much research, not only from a fundamental point of view, but also because of its importance in electrocatalysis and other reactions of industrial interest. Electron transfer is very often coupled with preceding or following chemical reactions, so that elucidation of the full reaction mechanism and kinetics is more complex. With the advent of hydrodynamic electrodes and, more recently, greatly improved ways of analysing electrical transients, significant developments in the study of electrode kinetics have occurred. These advances will be surveyed and future prospects indicated.

The surface concentration effect of the metal ion during the stripping step of ASV, in a complexing medium, is discussed in terms of determination of stability constants, from the results for Pb(II) + TETA system. Subsequently, stability constants of Cd(II) + carboxy-phenyliminodiacetic acid, phenylmethyliminodiacetic acid, pyridine-2,6-dicarboxylic acid and pyridine-2-carboxylic acid have been determined and the values compared with those obtained by other techniques.

Potassium Ion Selective Electrode with a PVC Membrane Applied to a Conductive Epoxy Support. A new technique for the construction of "all solid state" PVC membrane electrodes which consists of direct formation of the membrane on a support of silver loaded conductive epoxy is described. The response characteristics of a potassium electrode with the Corning 47731 7 sensor prepared by this technique are presented. The electrode shows performance similar to the conventional (with internal solution) electrode with the same sensor, but longer durability. The advantages and shortcomings of the present construction technique over the procedures previously described for the assembly of PVC membrane electrodes (of conventional or "coated-wire" types) are discussed.

ABSTRACT Green solutions of [CuL(H20)] [ClO4]2.H20 (L=C30H24N6; structure below) in acetonitrile slowly become red. The process can be followed by cyclic voltammetry and differential pulse polarography. An initial reversible one-electron redox process vanishes with time; concurrently another appears, at more negative potentials. This behaviour will be described and discussed. KEYWORDS: colour change in solution; cyclic voltammetry; differential pulse polarography

A direct polarographic method for EDTA determination based on the measurement of the anodic wave (DCP) or peak height (DPP) observed at +0.100 V, vs SCE, in the oxidation of the dropping mercury electrode in the presence of EDTA at pH=6.0 is described. The conditions for a simple and reproducible method using the standard additions technique for the analysis of this chelating agent in ophthalmic products are studied. Finally, the differential pulse polarographic method is applied to the analysis of EDTA in eye drops and contact lens wetting and cleaning solutions.