Novel Carbon Nanotube Paste Electrode for Simultaneous Determination of Norepinephrine, Uric Acid and D-Penicillamine

Abstract

The electro-oxidation of norepinephrine (NE), uric acid (UA), D-penicillamine (D-PA) and their mixture by modified carbon nanotube paste electrode of 2, 2'-[1, 2-ethanediylbis (nitriloethylidyne)]-bis-hydroquinone (EBNBH) has been studied using cyclic voltammetry, chronoamperometry and differential pulse voltammetry. In the mixture containing of NE, UA and D-PA, the three compounds can well separate from each other at the scan rate of 30 mVs−1 with potential differences of 190, 250 and 440 mV between NE - UA, UA – D-PA and NE – D-PA respectively, which was large enough to determine NE, UA and D-PA individually and simultaneously. Linear calibration plots were obtained over the concentration ranges of 0.1-1100.0 μM, 10.0-800.0 μM and 15.0-700.0 μM for NE, UA and D-PA respectively. The diffusion coefficient (D = 4.54×10-6 cm2 s–1), and the kinetic parameters such as electron transfer coefficient, (α = 0.41) and heterogenous rate constant, (k´ = 1.3 ×10-3 cm s-1) for NE were also determined using electrochemical approaches. The results were explained using the theory of electrocatalytic reactions at chemically modified electrodes. Further investigations of the modified carbon nanotube paste electrode show reproducible behavior and high level of stability.