Selective electrochemical determination of dopamine in the presence of ascorbic acid using sodium dodecyl sulfate micelles as masking agent

From differential pulse voltammetry, DPV, it was determined the electrochemical behaviour of dopamine, DA, and ascorbic acid, AA, using a carbon paste electrode, CPE, with the surfactant sodium dodecyl sulfate, SIDS, present at concentrations around the critical micellar concentration, CIVIC It is shown that without SDS in solution, the oxidation peak potential of AA, E-AA, and DA, E-DA, completely overlap, however when [SDS] > CMC separation is possible between them (E-AA-E-DA = 238 mV). Moreover, at variance with other proposed systems, the DA potential peak becomes less positive than AA potential peak. Therefore, separation of signals allows selective determination of DA even when AA is present in the same solution. Optimization of the experimental conditions permitted to obtain a calibration plot for the DA in the presence of the AA, having a 0.01-0.2 mM linear range, a detection limit of 5 mu M and a 0.04812 mu A mu M-1 sensitivity. This new approach was used effectively to determine dopamine in real pharmaceuticals obtaining satisfactory results. (C) 2007 Elsevier Ltd. All rights reserved.