Determination of Trace Amounts of Sulfamethizole Using a Multi-Walled Carbon Nanotube Modified Electrode: Application of Experimental Design in Voltammetric Studies

摘要

The present paper is the first report for the simultaneous investigation of various factors affecting the oxidation peak currents of sulfamethizole (SM) in a 0.20 M Britton-Robinson (B-R) buffer solution. Experimental factors (pH, multiwalled carbon nanotube amount, scan rate, step potential, and modulation amplitude) on voltammetric determination of SM were optimized simultaneously by a central composite rotatable design (CCRD). Then, in the optimized conditions, differential pulse voltammetry (DPV) was applied for selective determination of SM at the surface of a multi-walled carbon nanotube modified carbon paste electrode (MWCNT/CPE).The modified electrode showed enhanced effect on the oxidation peak current of SM. In these conditions the linear dynamic range for SM was from 0.10 up to 131.94 μM and the detection limit was found to be 14.31 nM. The characterization of MWCNT/CPE was carried out bycyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Also, linear sweep voltammetry (LSV) and chronocoulometry of SM were studied. Using these techniques, the diffusion coefficient (D = 4.91 × 10~(-5) cm~2 s~(-1)) and the kinetic parameters such as the electron transfer coefficient (α = 0.79) and exchange current density (j0 = 2.78 × 10~(-12) μA cm~(-2)) for SM were calculated. The proposed method was then successfully applied to the determination of SM in plasma samples.