Benzoquinone reduction on a lipid coated glassy carbon electrode has been studied in aqueous solutions employing spectroelectrochemical techniques. The intermediate species, benzoquinone anion radical (BQT(radical anion)) thus far believed to be unstable in aqueous solutions, has been shown to be rather stable in a lipid layer on a glassy carbon electrode, especially in a buffered solution. The kinetic parameters D-0 and k(0) for the oxidation reaction of benzoquinone anion radical (BQ(radical anion)) on a phosphatidylcholine (PC) coated electrode were determined to be 8.1 x 10(-6) cm(2) s(-1) and 3.2 x 10(-2) cm s(-1) respectively, by chronocoulometry. The electrochemical data showed that the reduction products of BQ are incorporated into the PC layer. The interaction of the reduction intermediates with PC was investigated in detail with FT-IR and NMR spectroscopy, which showed that the reduction product, the anion radical, was bound to the hydrogen bonded phosphate group in the PC molecule.