Determination of Oxyclozanide in Beef and Milk using High-Performance Liquid Chromatography System with UV Detector

This study was developed and validated for the determination of oxyclozanide residue concentrations in beef and commercial milk, using high-performance liquid chromatography system. Oxyclozanide was successfully separated on a reverse phase column (Xbridge-C(18), 4.6×250 mm, 5 µm) with a mobile phase composed of acetonitrile and 0.1% phosphoric acid (60:40, v/v%). This analytical procedure involved a deproteinization process using acetonitrile for beef and 2% formic acid in acetonitrile for commercial milk, dehydration by adding sodium sulfate to the liquid analytical sample, and a defatting process using n-hexane; after these steps, the extract was exposed to a stream of nitrogen dryness. The final extracted sample was dissolved in the mobile phase and filtered using a 0.45 µm syringe filter. This method had good selectivity and recovery (70.70±7.90-110.79±14.95%) from the matrices. The LOQs ranged from 9.7 to 9.8 µg/kg for beef and commercial milk. The recoveries met the standards set by the CODEX guideline.