LAUSR

ABSTRACT A simple electrochemical sensor for dopamine was developed based on activated carbon (AC) as a modifier for carbon paste electrode (CPE). The proposed electrode (AC-CPE) was used to study the electrocatalytic oxidation of dopamine by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). Firstly, the electrochemical behaviour of the modified electrode demonstrated that the substantial of the cathodic and anodic peak potentials were positively and negatively shifted, respectively; accompanied by an enhancement of current peak of DA. Then, the diffusion coefficient (D = 1.01 × 10−5 cm2 s−1) and the kinetic parameters such as the electron transfer coefficient (α = 0.48), apparent electron transfer rate constant (ks = 0.80 s−1) and catalytic reaction rate constant (kcat = 40.90 × 104 mol L−1 s−1) for dopamine at the surface of the AC-CPE were determined using electrochemical approaches. The AC−CPE showed favourable electron transfer kinetics and electro-catalytic activity towards oxidation/reduction of the dopamine. Differential pulse voltammetry (DPV) was used successfully for the determination of DA in the linear response range from 1.0 × 10−7 to 1.0 × 10−3 mol L−1 with a detection limit of 3.09 × 10−8 mol L−1. The AC−CPE offered high electro-catalytic activity in dopamine sensing individually and simultaneously in the presence of hydroquinone, catechol, paracetamol and phenol. These results demonstrated that the AC−CPE exhibited an excellent anti-interference property by peaks separation. The practical analytical utility of the AC−CPE is illustrated by dopamine determination in blood samples.