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

A covalently modified glassy carbon electrode with an α-alanine monolayer was fabricated and was applied to the electrocatalytic oxidation of ascorbic acid, reducing the overpotential by about 280 mV with an obviously increased current response. The catalytic current obtained from square-wave voltammetry was linearly dependent on ascorbic acid concentration in the range 2.0 × 10−5–5.0 × 10−3 mol L−1 with a correlation coefficient of 0.997. Owing to the catalytic effect of the modified film towards ascorbic acid, the modified electrode resolved the overlapped voltammetric responses of ascorbic 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 used to allow the determination of ascorbic acid in the presence of dopamine. The modified electrode showed good selectivity, stability and anti-fouling properties.