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 dea ctivated polythiophene (PT) film modified electrode were investigated. It w as found that DA displays nearly identical voltammetric response at both a bare and the modified electrode, while the voltammetric signal of AA is gre atly suppressed at the modified electrode due to the repulsion between it a nd the deactivated film. Various experimental parameters affecting the volt ammetric responses of DA and AA were studied. The modified electrode was de monstrated 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 calibra tion curve of DA was linear over the range of 0.8 mu M - 1.0 mM in the pres ence of 1.0 mM AA. The detection limit was 0.4 mu M.