Analytical Sciences

Abstract − Analytical Sciences, 17(8), 939 (2001).

Covalent Modification of Glassy Carbon Electrodes with beta-Alanine for Voltammetric Separation of Dopamine and Ascorbic Acid
Lei ZHANG,*  and Yu-Gang SUN**
*Department of Chemistry, University of Science and Technology of China, Hefei, Anhui, 230026, PR China
**Department of Chemistry, University of Washington, Seattle, WA, 98195-1700, USA
beta-Alanine was covalently grafted on a glassy carbon electrode (GCE) by amine cation radical formation in the electrooxidation process of the amino-containing compound. X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV) proved the immobilization of beta-alanine monolayer on GCE. The electrode shows strong electrocatalytic functions to dopamine (DA) and ascorbic acid (AA), reducing the overpotentials by 0.20 V and 0.23 V, respectively. Due to its different catalytic effects toward DA and AA, the modified electrode resolved the overlapping voltammetric responses of DA and AA into two well-defined voltammetric peaks by CV or differential pulse voltammetry (DPV), which can be used for the simultaneous determination of these species in a mixture. The catalytic peak current obtained from DPV was linearly related to DA and AA concentrations in the ranges of 4.0 x 10-6 - 5.0 x 10-4 mol/L and 2.0 x 10-5 - 6.0 x 10-3 mol/L with correlation coefficients of 0.997 and 0.995, respectively. The detection limits (3sigma) for DA and AA were 2.4 x 10-6 mol/L and 1.2 x 10-5 mol/L, respectively. The electrode shows good sensitivity, selectivity and stability, and has been applied to the determination of DA and AA simultaneously in samples with satisfactory results.