Amperometric determination of ascorbic acid at an electrodeposited redox polymer film modified gold electrode

A sensitive and selective electrochemical method for the determination of ascorbic acid was developed. It was shown that a hydrated osmium complex-containing redox polymer film can be electrodeposited at the gold electrode and it exhibits excellent electrocatalytic activity towards the oxidation of ascorbic acid. In contrast to a bare gold electrode, the oxidation current of ascorbic acid increased greatly and the oxidation peak potential shifted negatively to about 0.01 V (vs. SCE) at the modified electrode. Amperometric measurements were performed at an applied potential of 0.01 V and a linear response was obtained in the range of 2 - 400 muM with a limit of detection (LOD) of 0.6 muM (S/N = 3). The interference studies showed that the modified electrode exhibits excellent selectivity in the presence of large excess of uric acid and dopamine. The proposed procedure was successfully applied to the determination of ascorbic acid in human urine samples.