Novel 2,2′-[1,2-ethanediylbis(nitriloethylidyne)]-bis-hydroquinone double-wall carbon nanotube paste electrode for simultaneous determination of epinephrine, uric acid and folic acid

The electro-oxidation of epinephrine (EP), uric acid (UA), folic acid (FA), and their mixture has been studied by modified carbon nanotube paste electrode of 2,2'-[1,2-ethanediylbis(nitriloethylidyne)]-bishydroquinone using cyclic voltammetry. chronoamperometry and differential pulse voltammetry. This modified electrode exhibited potent and persistent electron mediating behavior followed by well-separated oxidation peaks towards EP, UA and FA with activation overpotential. For the ternary mixture containing EP. UA and FA the three compounds can be well separated from each other at the scan rate of 20 mV s(-1). The obtained catalytic peak current, was linearly dependent on the EP, UA and FA concentrations in the range of 0.7-1200 mu M. 25-750 mu M and 15-800 mu M and the detection limits for EP, UA and FA were 0.216 +/- 0.004, 8.8 +/- 0.2 and 11.0 +/- 0.3 mu M, respectively. The diffusion coefficient (D), and the kinetic parameters such as electron transfer coefficient, (alpha) and heterogeneous rate constant, (k') for EP were also determined using electrochemical approaches. The modified electrode showed good sensitivity, selectivity and stability, and was employed for the determination of EP, UA and FA in the real samples. (C) 2008 Elsevier B.V. All rights reserved.