Electrochemical and catalytic investigations of dopamine and uric acid by modified carbon nanotube paste electrode

The redox response of a modified carbon nanotube paste electrode of 2,2'-[1, 2-ethanediylbis(nitriloethylidyne)]-bis-hydroquinone was investigated. Mixture of dopamine (DA) and uric acid (UA), can be separated from one another with a potential difference of 180 mV between them at a scan rate of 25 mVs(-1) by cyclic voltammetry. These conditions are sufficient to allow determination of DA and UA both individually and simultaneously. The electrocatalytic currents increases linearly with the DA and UA concentrations in the ranges of 0.1-900 mu M and 20-650 mu M, and the detection limits for DA and UA, were 0.087 and 15 mu M. respectively. The diffusion coefficient (D/cm(2) s(-1) = 7.3 x 10(-6)) and the kinetic parameters such as the electron transfer coefficient, (alpha=0.32) and the heterogeneous rate constant, (k'/cm s(-1)=2.21 X 10(-3)) for DA were determined using electrochemical approaches. (c) 2008 Elsevier B.V. All rights reserved.