Carbon paste electrode incorporating 1-[4-(ferrocenyl ethynyl) phenyl]-1-ethanone for electrocatalytic and voltammetric determination of tryptophan

A carbon paste electrode spiked with 1-[4-ferrocenyl ethynyl) phenyl]-1-ethanone (4FEPE) was constructed by incorporation of 4FEPE in 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 tryptophan (Trp) in aqueous buffered solution. It has been found that under optimum condition (pH 7.00), the oxidation of Trp at the surface of such an electrode occurs at a potential about 200 mV less positive than at an unmodified carbon paste electrode. The kinetic parameters such as electron transfer coefficient, alpha and rate constant for the chemical reaction between Trp and redox sites in 4FEPE modified carbon paste electrode (4FEPEMCPE) were also determined using electrochemical approaches. The electrocatalytic oxidation peak current of Trp showed a linear dependent on the Trp concentrations and linear calibration curves were obtained in the ranges of 6.00 x 10(-6) M - 3.35 x 10(-3) M and 8.50 x 10(-7) M - 6.34 x 10(-5) M of Trp concentration with cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods, respectively. The detection limits (3 sigma) were determined as 1.80 x 10(-6) M and 5.60 x 10(-7) M by CV and DPV methods. This method was also examined as a selective, simple and precise new method for voltammetric determination of tryptophan in real sample.