Electrocatalytic Determination of 6-Mercaptopurine Using Multiwall Carbon Nanotubes Paste Electrode in the Presence of Methyldopa

The main purpose of this study is to develop a sensitive and selective modified carbon-paste electrode (CPE) with multiwall carbon nanotubes (MWCNTs) for the determination of 6-mercaptopurine (6-MP) in the presence of methyldopa (MD) as a mediator. Electrochemical methods, such as cyclic voltammetry, double step chronoamperometry and square wave voltammetry (SWV), used to study the characterization of the proposed modified electrode. The results show that MD can catalyze the oxidation of 6-MP in aqueous solution. Also, the catalytic rate constant (k), and diffusion coefficient (D) for 6-MP were estimated. The pick currents of 6-MP increased linearly with concentration in the ranges of 0.31–550 μmol L-1, with detection limit of 0.1 μmol L-1. The relative standard deviation (RSD %) for seven replicate measurements of 0.7 μmol L-1 6-MP was 1.6%. The prepared electrode is successfully applied for the voltammetric determination of 6-MP in pharmaceutical and biological samples.