DETERMINATION OF DOPAMINE IN SOLUTION OF ASCORBIC-ACID AT GRAPHITE-REINFORCEMENT CARBON ELECTRODES BY DIFFERENTIAL PULSE VOLTAMMETRY

Cyclic and differential pulse (DP) voltammograms of dopamine (DA) in Ringer's solution were measured at a graphite-reinforcement carbon (GRC) electrode. GRC is available as the lead of mechanical pencils. Cyclic voltammograms of DA exhibited two anodic peaks, at ca. -0.0 V and ca. 0.4 V vs. SCE, and a cathodic peak at 0.05 V vs. SCE in the solution of pH 6.8. Ascorbic acid (AA) presented an irreversible anodic wave at 0.2 V at pH 6.8. Voltammograms in the mixed solution of AA and DA were not a simple sum of each voltammogram, and hence were associated with chemical complications between AA and DA. DP voltammograms of the mixed solution had an anodic and a cathodic peak at ca. 0.05 V, which were stable during 4 days' soaking of the electrode in the solution. The anodic peak height was proportional to the concentration of DA in the range from 5.0×10-6 to 1.2×1O-4mol dm-3. DA could be determined quantitatively from a calibration curve in the presence of AA from 5 to 20 times larger than DA concentrations. © 1990, The Japan Society for Analytical Chemistry. All rights reserved.