Electrocatalytic oxidation of dopamine on 2,2′-[3,6-dioxa-1,8-octanediylbis(nitriloethylidyne)]-bis-hydroquinone modified carbon paste electrode

Abstract

A chemically modified carbon paste electrode with 2,2′-[3,6-dioxa-1,8-octanediylbis(nitriloethylidyne)]-bis-hydroquinone (DOH) was employed to study the electrocatalytic oxidation of dopamine (DA) in buffer solution using cyclic voltammetry (CV), square wave voltammetry (SWV) and chronoamperometry (CHA). The diffusion coefficient (D = 7.4 × 10⁻⁶ cm² s⁻¹), and the kinetic parameter such as the electron transfer coefficient (α = 0.33) of DA oxidation at the surface of 2,2′-[3,6-dioxa-1,8-octanediylbis(nitriloethylidyne)]-bis-hydroquinone modified carbon paste electrode (DOHMCPE) was determined using electrochemical approaches. It has been found that under an optimum condition (pH 7.0), the oxidation of DA at the surface of the modified electrode occurs at a potential about 290 mV less positive than that of an unmodified carbon paste electrode. The catalytic oxidation peak currents showed a linear dependence on the DA concentration and linear analytical curves were obtained in the ranges of 3.0 × 10⁻⁵ M–2 × 10⁻³ M of DA with SWV. The detection limits (2σ) were determined to be 3.2 × 10⁻⁶ M. This method was also used for the determination of DA in a pharmaceutical preparation (injection) by the standard addition method.