Simultaneous determination of dopamine, uric acid, and folic acid by a modified TiO2 nanoparticles carbon paste electrode

The electrochemical behavior of dopamine (DA) was studied at the surface of a 2,2-[1,2 buthanediylbis(nitriloethylidyne)]-bis-hydroquinone/TiO2 nanoparticles modified carbon paste electrode (BQTMCPE) in aqueous media using voltammetric and chronoamperometric techniques. It was found that under optimum conditions (pH 8.0), the oxidation of DA at the surface of such an electrode occurred at about 220 mV lower than that of an unmodified carbon paste electrode (CPE). Using differential pulse voltammetry (DPV), a highly selective and simultaneous determination of DA, uric acid (UA), and folic acid (FA) was explored at the modified electrode. DPV peak currents of DA, UA, and FA increased linearly with their concentrations in the ranges of 1.0-900.0 mu M, 200.0-1500.0 mu M, and 200.0-2700.0 mu M, respectively, and the detection limits for DA, UA, and FA were 0.3 mu M, 12.0 mu M, and 32.0 mu M, respectively. This method was also used for the determination of DA in pharmaceutical preparation (DA injection) by the standard addition method.