Electrocatalytic determination of ascorbic acid at the surface of 2,7-bis(ferrocenyl ethyl)fluoren-9-one modified carbon paste electrode

A chemically modified carbon paste electrode with 2,7-bis(ferrocenyl ethyl)fluoren-9-one (2,7-BFEFMCPE) was employed to study the electrocatalytic oxidation of ascorbic acid in aqueous solution using cyclic voltammetry, differential pulse voltammetry and chronoamperometry. The diffusion coefficient (D = 1.89 x 10(-5) cm(2) s(-1)), and the kinetic parameter such as the electron transfer coefficient, alpha (=0.42) of ascorbic acid oxidation at the surface of 2,7-BFEFMCPE was determined using electrochemical approaches. It has been found that under an optimum condition (pH 7.00), the oxidation of ascorbic acid at the surface of such an electrode occurs at a potential about 300 mV less positive than that of an unmodified carbon paste electrode. The catalytic oxidation peak currents show a linear dependence on the ascorbic acid concentration and linear analytical curves were obtained in the ranges of 8.0 x 10(-5) M-2.0 x 10(-3) M and 3.1 x 10(-5) M-3.3 X 10(-3) M of ascorbic acid with correlation coefficients of 0.9980 and 0.9976 in cyclic voltammetry and differential pulse voltammetry, respectively. The detection limits (2 delta) were determined to be 2.9 x 10(-5) M and 9.0 x 10(-6) M with cyclic voltammetry and differential pulse voltammetry, respectively. This method was also examined for determination of ascorbic acid in pharmaceutical preparations.