Carbon paste electrode spiked with ferrocene carboxylic acid and its application to the electrocatalytic determination of ascorbic acid

A carbon paste electrode spiked with ferrocene carboxylic acid (FCAMCPE) was constructed by incorporation of ferrocene carboxylic acid in a graphite powder–paraffin oil matrix. It has been shown by direct current cyclic voltammetry and double step chronoamperometry that this electrode can catalyze the oxidation of ascorbic acid in aqueous buffered solution. It has been found that under optimum conditions (pH 5) the oxidation of ascorbic acid at the surface of such an electrode occurs at a potential about 248 mV less positive than at an unmodified carbon paste electrode. The catalytic oxidation peak current was linearly dependent on the ascorbic acid concentration and a linear calibration curve was obtained in the range 3.48×10−5–0.49×10−3 M of ascorbic acid with a correlation coefficient of 0.9997. The detection limit (3σ) was determined as 1.08×10−5 M.