The effect of the supporting electrolyte on the voltammetric determination of the veterinary drug nitroxinil

In this work, a new approach for the determination of the veterinary drug nitroxinil is presented, and its electrochemical behavior is investigated as well as voltammetric determination based on its oxidation signal is proposed. A glassy carbon electrode (GCE) was used as an electrochemical sensor for the determination of this compound, and a square-wave voltammetric (SWV) technique with the optimized parameters was applied for the quantification of nitroxinil. The effect of the supporting electrolytes, such as Britton-Robinson buffer solution (BRBS), citrate buffer solutions (CBS), and hydrochloric acid-potassium chloride buffer solutions (HCl-KClBS), on the SWV determinations of nitroxinil was investigated, and the experiments showed that the supporting electrolyte has a significant effect on the nitroxinil determination. The highest analytical SWV response of nitroxinil was obtained in acidic medium of the investigated supporting electrolytes, i.e. in the BRBS at pH 2.0, the CBS at pH 2.0, and the HCl-KClBS at pH 1.8. The corresponding current at ca. +1.3 V vs. Ag/AgCl/3 mol L−1 KCl reference electrode increased linearly with the concentration of nitroxinil within two linear dynamic ranges (LDR) in each supporting electrolyte solution. The lowest limit of detection (LOD) and quantification (LOQ) for nitroxinil were achieved in the BRBS at pH 2.0 (LOD = 0.28 μmol L−1 and LOQ = 0.93 μmol L−1). In addition, the analytical parameters obtained from calibration curves indicated the best sensitivity in the BRBS at pH 2.0 (0.124 μA L μmol−1). Cyclic voltammetric (CV) experiments showed that the electrode reaction of nitroxinil is irreversible (oxidation peak at ca. +1.3 V) and diffusion-controlled in each supporting electrolyte solution.