Simultaneous determination of epinephrine and uric acid at a gold electrode modified by a 2-(2,3-dihydroxy phenyl)-1, 3-dithiane self-assembled monolayer

In the present paper, the use of a gold electrode modified by 2-(2,3-dihydroxy phenyl)-1,3-dithiane self-assembled monolayer (DPDSAM) for the determination of epinephrine (EP) and uric acid (UA) was described. Initially, cyclic voltammetry was used to investigate the redox properties of this modified electrode at various scan rates. The apparent charge transfer rate constant, k(s), and transfer coefficient, alpha, were calculated. Next, the mediated oxidation of EP at the modified electrode was described. At the optimum pH of 8.0, the oxidation of EP occurs at a potential about 155 mV less positive than that of an unmodified gold electrode. The values of electron transfer coefficients (alpha = 0.356), catalytic rate constant (k = 1.624 x 10(4) M-1 s(-1)) and diffusion coefficient (D = 1.04 x 10(-6) cm(2) s(-1)) were calculated for EP, using electrochemical approaches. Based on differential pulse voltammetry, the oxidation of EP exhibited a dynamic range between 0.7 and 500.0 mu M and a detection limit (3 sigma) of 0.51 mu M. Furthermore, simultaneous determination of EP and UA at the modified electrode was described. Finally, this method was used for the determination of EP in EP ampoule. (C) 2010 Elsevier B.V. All rights reserved.