Rapid determination of ascorbic acid, dehydroascorbic acid, and total vitamin C by electrochemiluminescence with a thin-layer electrochemical cell

This paper reports on a rapid and sensitive method for the simultaneous determination of ascorbic acid (H(2)A), dehydroascorbic acid (DHA), and total vitamin C by electrochemiluminescence (ECL) using a thin-layer electrochemical cell. Significant ECL signals can be generated by the anodic oxidation of Ru(bpy)(3)(2+) in the presence of H(2)A or DHA in pH 8.8 phosphate buffer solution. Because of the extremely small dead volume of the thin-layer cell (approximately 1.5 mu L), almost all amount of H(2)A is assumed to be completely oxidized to DHA with a short pre-electrolysis step. As a result, it is possible to determine the reductive vitamin C (H(2)A) by square wave voltammetry before the pre-electrolysis step, while total vitamin C (sum of H(2)A and DHA) is able to be determined at a subsequent ECL step. The method was employed for the determination of vitamin C in commercial beverages with the analytical results in good agreement with the certified values.