FIA determination of ascorbic acid at low potential using a ruthenium oxide hexacyanoferrate modified carbon electrode.

The anodic oxidation of ascorbic acid on a ruthenium oxide hexacyanoferrate modified electrode was characterized by cyclic voltammetry. On this modified surface, the electrocatalytic process allows the determination of ascorbic acid to be performed at 0.0 V and pH 6.9 with a limit of detection of 2.2 microM in a flow injection configuration. Under this experimental condition, no interference from glucose, nitrite and uric acid was noticed. Lower detection limit values were obtained by measuring flow injection analysis (FIA) responses at 0.4V (0.14 microM), but a concurrent loss of selectivity is expected at this more positive potential. Under optimal FIA operating conditions, the linear response of the method was extended up to 1 mM ascorbic acid. The repeatability of the method for injections of a 1.0 mM ascorbic acid solution was 2.0% (n=10). The usefulness of the method was demonstrated by an addition-recovery experiment with urine samples and the recovered values were in the 98-104% range.