Application of a modified carbon nanotube paste electrode for simultaneous determination of epinephrine, uric acid and folic acid

A novel 5-amino-3',4'-dimethoxy-biphenyl-2-ol (5ADMB) modified carbon nanotube paste electrode (5ADMBCNPE) was first prepared for the determination of epinephrine (EP). Cyclic voltammetry (CV) was used to investigate the electrochemical properties of the proposed electrode towards the oxidation of EP. It has been found that under an optimum condition (pH 7.0), the oxidation of EP at the surface of the modified electrode occurs at a potential of about 160 mV less positive than that of an unmodified carbon paste electrode. The diffusion coefficient (D = 1.18 x 10(-5) cm(2) s(-1)), and electron transfer coefficient (alpha = 0.53) of EP at the surface of 5ADMBCNPE were determined using electrochemical approaches. Using square wave voltammetry (SWV) a linearity between the oxidation peak current and the EP concentration was obtained in the range of 0.4 to 900.0 mu M with a detection limit (3 sigma) of 88.0 nM. Also, SWV was used for simultaneous determination of EP, uric acid (UA) and folic acid (FA) at the modified electrode.