CHARACTERIZATION OF SMALL NOBLE-METAL MICROELECTRODES BY VOLTAMMETRY AND ENERGY-DISPERSIVE X-RAY-ANALYSIS

Construction and characterization of platinum and gold electrodes with total structural diameters of 1-2 mum is described. These small volta mmetric probes have been constructed by direct electroreduction of nob le metals onto the tips of etched carbon fiber microdisk electrodes. V oltammetry, electron microscopy, energy-dispersive X-ray analysis, and pulsed amperometric detection have been used to characterize these el ectrodes. Dopamine concentrations have been determined over a range of 10(-4)-10(-3) M in a biological buffer system which contains 25 mM gl ucose, a compound known to adsorb strongly to electrodes. Amperometric monitoring at a constant potential with these small electrodes result s in signal decay of 20-40% in a 10-min experiment. Pulsed amperometri c detection minimizes electrode fouling, resulting in 5% or less signa l decay over the same 10-min period.