Redox cycling with facing interdigitated array electrodes as a method for selective detection of redox species

A pair of interdigitated ultramicroelectrodes (UMEs) is used to electrochemically detect a weak reductor (dopamine) in the presence of a stronger one (K(4)[Fe(CN)(6)]). In the mixture of both reductors, one of the two interdigitated electrodes (the generator electrode) is used to oxidize both species at 700 mV vs. Ag/AgCl, followed by subsequent (selective) reduction of the oxidized dopamine at 400 mV. A regenerated dopamine molecule can thus be oxidized several times (redox cycling) and enable selective detection even in the presence of the stronger reductor. In order to obtain high redox cycling efficiency, we designed and realized platinum electrodes with widths of 2 and 4 microm and spacing of 2 microm, which gave redox cycling efficiencies of 9 and 4 respectively. Using this electrode design, a dopamine/K(4)[Fe(CN)(6)] selectivity of 2 could be obtained.