Simultaneous determination of dopamine and ascorbic acid at glutamic acid modified graphite electrode

This paper reports the preparation of the glutamic acid chemically modified graphite electrode and its electro catalytic function toward dopamine and ascorbic acid. The overlapped oxidation peaks of dopamine and ascorbic acid can be separated up to about 200 mV, which is large enough to determine both of them simultaneously in a mixture. The catalytic peak currents obtained from the cyclic voltammograms are linearly related to both dopamine and ascorbic acid concentrations in the ranges of 6.0 x 10(-6) -8.0 x 10(-4) mol/L with correlation coefficient of 0.9976 for dopamine and 4.0 x 10(-5)-0.1 mol/L with correlation coefficient of 0.9982 for ascorbic acid. The detection limits (3 sigma) for dopamine and ascorbic acid are 1.8 x 10(-6) mol/L and 1.3 x 10(-5) mol/L, respectively. The modified electrodes showed high catalyticability and good stability. The proposed method has been successfully applied to the simultaneous determination of dopamine and ascorbic acid in samples.