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

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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]=5mM it was adsorption-controlled. Furthermore, in the absence of SDS it was observed that the DA, AA and UA oxidation peaks’ potentials fully overlapped. However, when the [SDS]=5mM, it became clear that the DA's oxidation peak, EDA, shifted to less positive potential values, while oxidation potentials EAA and EUA corresponding to AA and UA respectively, moved to more positive values, thereby obtaining effective peak's separations of EAA−EDA=272mV and EUA−EDA=171mV. 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 8–134μM, a sensitivity of 106.58±0.99μAmM−1, a detection limit of 3.70±0.01μM, and a quantification limit of 12.05±0.04μM, which made it possible to effect DA's quantification on a commercial pharmaceutical sample with a recovery average of 94%.