Electrochemical and catalytic investigations of epinephrine, acetaminophen and folic acid at the surface of titanium dioxide nanoparticle-modified carbon paste electrode

In the present paper, the use of a carbon paste electrode modified with 1-(4-(1, 3-dithiolan-2-yl)-6, 7-dihydroxy-2-methyl-6, 7-dihydrobenzofuran-3-yl)ethanone (DDE) and TiO2 nanoparticles prepared by a simple and rapid method was described. The modified electrode showed excellent properties for electrocatalytic oxidization of epinephrine (EP), acetaminophen (AC) and folic acid (FA). The apparent charge transfer rate constant, k (s) = 1.14 s(-1), and transfer coefficient, alpha = 0.54, for electron transfer between the modifier and carbon paste electrode were calculated. It has been found that under optimum condition (pH = 7.0) in cyclic voltammetry, the oxidation of EP occurs at a potential about 280 mV less positive than that of an unmodified carbon paste electrode. The values of transfer coefficients (alpha = 0.46), catalytic rate constant (k = 1.2 x 10(4) M-1 s(-1)) and diffusion coefficient (D = 2.70 x 10(-5) cm(2) s(-1)) were calculated for EP. Differential pulse voltammetry (DPV) exhibited two linear dynamic ranges of 0.5 to 50.0 mu M and 50.0 to 1,000 mu M for EP. This modified electrode is quite effective not only for the detection of EP, AC and FA but also for the simultaneous determination of these species in a mixture. The limit of detection for EP, AC and FA is 0.10, 1.80 and 2.36 mu M, respectively.