ELECTROCHEMICAL-BEHAVIOR OF ALPHA-TOCOPHEROL IN A THIN-FILM OF NUJOL,A MODEL OF ADIPOSE-TISSUE

It has been shown that cyclic voltammetry (CV) on a paste electrode, m ade of graphite powder and an electroinactive oily material containing a redox active compound, in an aqueous electrolytic solution provided a well-defined cyclic voltammogram of the compound. The electrochemic al oxidation of alpha-tocopherol (I) in the Nujol component of a Nujol carbon paste electrode (CPE) produced both dienone cation (III) and a lpha-tocopherylquinone (V), which increased on repeated cyclic voltamm ograms. One-electron oxidation of I took place during a positive sweep in the potential region between 100 and 300 mV/SCE. Subsequent oxidat ion to cation m took place in the more positive potential region. Thes e results were obtained using a series of CVs with increasing positive switching potentials (PSPs). CV curves of I at high concentrations in Nujol indicated that (1) the ring-opening reaction of III to produce V takes place in lower ratio than at low concentrations, and (2) the a mount of I which is involved in the electrochemical reaction is invers ely proportional to the concentration of I in the Nujol component of t he CPE. The observed phenomena are discussed on the basis of the mobil ity of counter-ions in Nujol.