Voltammetric determination of dopamine in a mixture of dopamine and ascorbic acid at a deactivated polythiophene film modified electrode

The voltammetric responses of dopamine (DA) and ascorbic acid (AA) at a deactivated polythiophene (PT) film modified electrode were investigated. It was found that DA displays nearly identical voltammetric response at both a bare and the modified electrode, while the voltammetric signal of AA is greatly suppressed at the modified electrode due to the repulsion between it and the deactivated film. Various experimental parameters affecting the voltammetric responses of DA and AA were studied. The modified electrode was demonstrated to be very useful in selectively determining DA in a mixture of DA and AA. At a 0.5 mu m deactivated PT film modified electrode the calibration curve of DA was linear over the range of 0.8 mu M - 1.0 mM in the presence of 1.0 mM AA. The detection limit was 0.4 mu M.