Abstract

An electrochemical analysis of B6 vitamins has been presented. The electrooxidation of vitamin B6 group and related compounds has been performed at neutral pH using glassy carbon and gold electrodes. Irreversible electrochemical processes are observed for these substances by cyclic voltammetry. The rate of the first or second electron transfer (E) and/or the presence of chemical steps (C) determinate the electrode process (with schemes classified as EC, CE, ECE, ECEC, mostly). In numerous cases the values of Ep-Ep/2 suggest the first electron transfer (apparent αna < 1) as the responsible of the kinetic control of the process. An approximation for the reaction schemes of these compounds on these solid electrodes was also presented suggesting a surface interaction. In the oxidation on glassy carbon, the presence of oxygenated species at sub-monolayer level must play a determining role, which is revealed in particular by analyzing the behavior of the aldehydes studied (PLP, PL, P). The electroactive species must be in their hydrated ionized form.
The compounds of the series showed oxidation waves in a glassy carbon electrode at potentials that are relatively low compared to the oxidation potential of the same electroactive groups on this electrode. This behavior suggests an activation of the oxidation of the vitamin B-6 derivatives. In the same way the compounds of the series showed oxidation waves in a polycrystalline gold electrode. In some cases, an oxidation process at a less anodic potential is also observed showing efficient electrocatalytic behaviour