Separation of anodic peaks of ascorbic acid and dopamine at an ct-alanine covalently modified glassy carbon electrode

A covalently modified glassy carbon electrode with an a-alanine monolayer w as fabricated and was applied to the electrocatalytic oxidation of ascorbic acid, reducing the overpotential by about 280 mV with an obviously increas ed current response. The catalytic current obtained from square-wave voltam metry was linearly dependent on ascorbic acid concentration in the range 2. 0 x 10(-5)-5.0 x 10(-3) mol L-1 with a correlation coefficient of 0.997. Ow ing to the catalytic effect of the modified film towards ascorbic acid, the modified electrode resolved the overlapped voltammetric responses of ascor bic acid and dopamine into two well-defined square wave voltammetric peaks with peak-to-peak separation in potentials of about 180 mV. This can be use d to allow the determination of ascorbic acid in the presence of dopamine. The modified electrode showed good selectivity. stability and anti-fouling properties.