Voltammetric assay of the anthelmintic veterinary drug nitroxynil in bulk form and formulation at a mercury electrode

Abstract

The electrochemical behavior of the anthelmintic veterinary drug nitroxynil at the mercury electrode was studied in a series of Britton-Robinson universal buffer of pH 1.9–11 containing 20% (v/v) ethanol using dc-polarography cyclic voltammetry and controlled-potential coulometry. The voltammograms exhibited two irreversible cathodic steps over the pH range 1.9–10.2; the height of the first step is double that of the second one. Controlled-potential coulometry in the B–R universal buffer of pH 1.9–10 at a mercury pool working electrode revealed the consumption of four and two electrons via the first and second reduction steps, respectively, which attributed to reduction of the NO 2 group to the hydroxylamine stage (first step), and then to the amine stage (second step). Three voltammetric analytical procedures including dc-polarography, differential-pulse adsorptive stripping voltammetry and square-wave adsorptive stripping voltammetry were optimized for the direct determination of bulk nitroxynil. The three proposed procedures were applied for analysis of bulk nitroxynil with limits of detection of 3 × 10 −5, 1.31 × 10 −8 and 8.4 × 10 −10 M and limits of quantification of 1 × 10 −5, 4.36 × 10 −8 and 2.80 × 10 −9 M, respectively. The three procedures were successfully applied to the determination of nitroxynil in formulation (Dovenix, 25% nitroxynil injection solution) without the necessity for sample pretreatment and/or time-consuming extraction steps prior to the analysis.