Electrochemical quantification of dopamine in the presence of ascorbic acid and uric acid using a simple carbon paste electrode modified with SDS micelles at pH 7

Dopamine's (DA) electrochemical behavior was studied using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in the presence of ascorbic acid (AA) and uric acid (UA), using a carbon paste electrode (CPE) modified with sodium dodecyl sulfate (SDS) micelles, at pH 7 by a rather simple immersion process. The results proved that in the absence of SDS DA oxidation was diffusion-controlled, whereas when the [SDS] = 5 mM it was adsorption-controlled. Furthermore, in the absence of SDS it was observed that the DA, M and UA oxidation peaks' potentials fully overlapped. However, when the [SDS] = 5 mM, it became clear that the DA's oxidation peak, E-DA, shifted to less positive potential values, while oxidation potentials E-AA and E-UA corresponding to AA and UA respectively, moved to more positive values, thereby obtaining effective peak's separations of E-AA E-DA = 272 mV and E-UA - E-DA = 171 mV. It is shown that the electrochemical determination of dopamine in the presence of both AA and UA using the SDS-modified CPE, displayed usable analytic parameters, namely: a linearity range of 8-134 mu M, a sensitivity of 106.58 +/- 0.99 mu A mM(-1), a detection limit of 3.70 +/- 0.01 mu M, and a quantification limit of 12.05 +/- 0.04 mu M, which made it possible to effect DA's quantification on a commercial pharmaceutical sample with a recovery average of 94%. (C) 2012 Elsevier Ltd. All rights reserved.