CATALYTIC-OXIDATION OF DOPAMINE AT A MICRODISK PLATINUM-ELECTRODE MODIFIED BY ELECTRODEPOSITION OF NICKEL HEXACYANOFERRATE AND NAFION(R)

A chemically modified microelectrode has been prepared successfully by means of electrodepositing nickel hexacyanoferrate(II-III) on a micro disk platinum electrode. This modified electrode could catalyze the ox idation of dopamine and, moreover, eliminate the electrode poisoning c aused by the electrochemical polymerization of dopamine at the bare pl atinum electrode. However, the oxidation of ascorbic acid could also b e catalyzed at this modified electrode, thus interfering with the elec trochemical response of dopamine. When the modified electrode was furt her covered with Nafion(R) membrane, the interference could be erased. The catalytic currents increased linearly with the concentration of d opamine in the range of 1.0 X 10(-4) to 1.5 X 10(-2) M. Such a microdi sk modified platinum electrode could be used for the determination of dopamine. In addition, the reaction rate constant of dopamine at the m odified electrode was evaluated by using a rotating disk electrode.