Voltammetric determination of dopamine in the presence of ascorbic acid at a chemically modified electrode

A Nafion/ruthenium oxide pyrochlore chemically modified electrode (CME) was used for the selective determination of dopamine (DA) in the presence of a high concentration of ascorbic acid by square wave voltammetry. Compared to a bare glassy carbon electrode, the CME exhibits an apparent shift of the oxidation potentials in cathodic direction and a marked enhancement of the current response. The selective sensing of DA is achieved by combining the electrocatalytic function of the ruthenium oxide pyrochlore catalyst with the charge-exclusion and preconcentration features of Nafion. With a preconcentration time of 60 s at a potential of -0.3 V (vs. Ag/AgCl), linear calibration plots are obtained for dopamine in 0.1 M, phosphate buffer (pH 7.4) over 0-20 mu M with a detection limit (3 sigma) of 0.1 mu M.