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 bo th of them simultaneously in a mixture. The catalytic peak currents obtaine d from the cyclic voltammograms are linearly related to both dopamine and a scorbic 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 detect ion 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 c atalyticability and good stability. The proposed method has been successful ly applied to the simultaneous determination of dopamine and ascorbic acid in samples.