Voltammetric determination of ethionamide in pharmaceutical formulations and human urine using a boron-doped diamond electrode

Abstract

This work reports a simple and low cost voltammetric approach comprising a boron-doped diamond electrode (BDDE) to determine the antibiotic ethionamide (ETO). Cyclic voltammetry studies revealed that ETO exhibits an irreversible reduction peak at -0.95 V and an irreversible oxidation peak at +1.4 V onto BDDE (vs. saturated Ag/AgCl reference electrode) in Britton-Robinson buffer solution (pH 5.0, 0.1 mol L-1 ). Different voltammetric scan rates (from 10 to 150 mV s-1 ) suggested that the reduction of ETO on the BDDE surface is a diffusion-controlled process. Square wave voltammetry (SWV) optimized conditions showed a linear response to ETO from 1.00 to 80.0 μmol L-1 (R2 = 0.998) with a limit of detection of 0.294 μmol L-1 and limit of quantification of 0.980 μmol L-1 . The developed square wave voltammetric method was successfully used in the determination of ETO in human urine and pharmaceutical formulation. The ETO quantification results in pharmaceutical tablets obtained by SWV-BDDE were comparable to those found by official analytical protocols.