HIGHLY SELECTIVE ELECTROCHEMICAL DETECTION OF DOPAMINE USING INTERDIGITATED ARRAY ELECTRODES MODIFIED WITH NAFION POLYESTER IONOMER LAYERED FILM

The highly selective electrochemical detection of dopamine has been developed using an interdigitated microarray (IDA) electrode coated with Nafion and polyester ionomer (Kodak AQ29D) layered films. Because high redox cycling of dopamine can be maintained in the AQ29D bottom layer, a low detection limit of 50 nmol/dm3 is obtained. Since the upper Nafion layer prevents L-ascorbic acid from diffusing into the AQ29D layer, the acid concentration in this layer rapidly decreases when potentiostating one IDA electrode (anode) above and the other (cathode) below the redox potential of dopamine. This is because L-ascorbic acid molecules in the AQ29D layer are removed quickly by the electrochemical or electrocatalytic oxidation at the anode. On the other hand, almost all of the oxidized dopamine molecules are reduced at the cathode, which maintains a constant dopamine concentration in the film during measurement. After the potential step, the influence Of L-ascorbic acid is almost completely eliminated within a few seconds due to the reduction in acid concentration in the modified layer. As a result, dopamine can be detected quantitatively at the cathode in the presence of 100-fold excess Of L-ascorbic acid.