Voltammetric determination of l-cysteic acid on a 1-[4-(ferrocenyl-ethynyl)phenyl]-1-ethanone modified carbon paste electrode
The electrochemical behaviour of L-cysteic acid was studied at the surface of 1-[4-(ferrocenyl-ethynyl)phenyl]-1-ethanone modified carbon paste electrode (4FEPEMCPE) in aqueous media using cyclic voltammetry and double step potential chronoamperometry. It has been found, that under optimum condition (pH 7.00) in cyclic voltammetry, the oxidation of L-cysteic acid at the surface of 4FEPEMCPE is occurred at a potential about 220 mV less positive than that an unmodified carbon paste electrode. The kinetic parameters such as electron transfer coefficient, α, and catalytic reaction rate constant, K/h, were also determined using electrochemical approaches. The electrocatalytic oxidation peak current of L-cysteic acid showed a linear dependent on the L-cysteic acid concentration and linear calibration curves were obtained in the ranges of 9 × 10-5 - 6.2 × 10-3 M and 2.0 × 10-7 - 1.17 × 10-5 M of L-cysteic acid concentration with cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods, respectively. The detection limits (3σ) were determined equal to 2.3 × 10-5 M and 8.7 × 10-8 M by CV and DPV methods. This method was also examined as a selective, simple and precise new method for voltammetric determination of L-cysteic acid in serum of patient's blood with migraine disease.
KEY WORDS: 1-[4-(Ferrocenyl-ethynyl)phenyl]-1-ethanone, L-Cysteic acid, Electrocatalysis, Cyclic voltammetry, Differential pulse voltammetry, Chronoamperometry
Bull. Chem. Soc. Ethiop. 2008, 22(2), 173-182.