Electrochemical and spectroscopic study of vitamin D2 by in situ thin layer CD spectroelectrochemistry

The electrooxidation of vitamin D2 (VD2) was studied by cyclic voltammetry and in situ circular dichroic (CD) spectroelectrochemistry for the first time. The mechanism of electrooxidation and some useful kinetic and adsorption parameters were obtained. The results showed that the oxidation of VD2 in ethanol solution is an irreversible diffusion controlled process following a weak adsorption of the electroinactive product at a glassy carbon electrode, which blocks the electrochemical reaction. The electrooxidation occurs mainly at the triene moieties of the VD2 molecule. The CD spectroelectrochemical data were treated by the double logarithm method together with nonlinear regression, from which the formal potential E0=1.08 V, αn=0.245, the standard electrochemical rate constant k0=4.30(±0.58)×10−4 cm s−1, and the adsorption constant β=1.77(±0.25) were obtained.