Anodic Adsorptive Stripping Voltammetric Determination of Rafoxanide on Glassy Carbon Electrode

The development of easy, accurate, reliable technique which is characterized by low cost, minimal sample pre-treatment, and short analysis time to monitor RFX residues in milk samples before distribution to consumers.

Literature survey reveals several analytical methods, including high-performance liquid chromatography (HPLC), ultra-performance liquid chromatography (UPLC) and thin-layer chromatography (TLC)-densitometry. These methods are time consuming, require additional steps like preconcentration or multisolvent extraction, trained technicians, and expensive instruments.

The electrochemical analysis of RFX was effectively established by the adsorptive stripping method on GCE due to the effective interfacial accumulation of RFX on the electrode surface. The RFX adsorptive accumulation is followed by electrochemical measurement of the accumulated analyte.

The electrochemical oxidation of RFX was studied at glassy carbon electrodes (GCE) in Britton-Robinson buffer (BR) solutions over the pH range from 2.0-12.0 using cyclic and differential pulse voltammetry (DPV). The oxidation of the drug was accomplished in a single irreversible, adsorption-controlled step within the pH range 4.0-9.0. Therefore, the application of GCE for a sensitive and selective quantification of RFX by adsorptive stripping voltammetry was reported. This format was satisfactorily applied for the determination of RFX in bovine milk. Limit of detection (LOD) of 1.25 μg kg-1 of milk and mean recoveries of 97.8 to 107.5% were achieved.

The proposed method might be competitive with the HPLC techniques. The detection limit found for RFX on GCE for milk samples, after medium exchange, was well below the MRLs, the maximum concentration of a veterinary drug residue legally permissible in food, are proposed by the European Medicines Agency.