Carbon nanoparticles and a new derivative of hydroquinone for modification of a carbon paste electrode for simultaneous determination of epinephrine and acetaminophen

A carbon paste electrode modified with a novel derivative of hydroquinone (DH), 2,2'-[1,2-ethanediylbis(nitrilomethylidyne)]-bishydroquinone, has been used to study the electrocatalytic oxidation of epinephrine (EP). In this work carbon nanoparticles (CNs) were used for improvement of electrochemical properties. The apparent charge transfer rate constant, k(s) = 2.03 +/- 0.15 s(-1), and transfer coefficient, alpha = 0.46, for electron transfer between the modifier and the carbon paste electrode were calculated. It has been found that under an optimum condition (pH = 7.0) in cyclic voltammetry, the oxidation of EP occurs at a potential about 222 mV less positive than that of an unmodified carbon paste electrode. The values of the transfer coefficient (alpha = 0.46), catalytic rate constant (k = 5.03 x 10(3) M-1 s(-1)) and diffusion coefficient (D = 4.67 x 10(- 6) cm(2) s(-1)) were calculated for EP. Differential pulse voltammetry (DPV) exhibited two linear dynamic ranges of 5.0 to 20.0 mu M and 20.0 to 600.0 mu M for EP. This modified electrode was quite effective not only to detect EP and acetaminophen (AC) but also in simultaneous determination of these species in a mixture. The lower limits of detection for EP and AC are obtained as 1.0 and 12.0 mu M, respectively.