Glassy carbon electrode modified with poly(dibromofluorescein) for the selective determination of dopamine and uric acid in the presence of ascorbic acid

We are presenting an electrochemical sensor for the simultaneous determination of dopamine (DA) and uric acid (UA) in the presence of even high concentrations of ascorbic acid (AA). It based on a glassy carbon electrode modified with an electroactive film of polymerized dibromofluorescein. The electrochemical behaviors of DA and UA were studied by cyclic voltammetry using the modified electrode. It exhibits excellent electrocatalytic activity towards the oxidation of the two analytes. Most notably, the oxidation potentials differ by 180 and 200 mV between AA-DA and DA-UA, respectively. Thus, excellent selectivity towards the oxidation of DA and UA in the presence of even high concentrations of AA is accomplished. Under the optimum conditions, the anodic peak currents are linearly related to the concentrations of DA and UA in the range from 0.2 to 200 mu mol L-1 and from 1.0 to 250 mu mol L-1, respectively. The detection limits for DA and UA are 0.03 mu mol L-1 and 0.2 mu mol L-1, respectively (at an S/N of 3). The method has good selectivity and sensitivity and was successfully applied to the simultaneous determination of DA and UA in spiked human serum.