Development of high-performance liquid chromatography for the determination of carbadox and olaquindox in animal feed

High-performance liquid chromatography (HPLC) method with UV detection (373 nm) was developed for the determination of carbadox and olaquindox in animal feed. Among three different columns (LichroCART Purosphere RP-18, Waters Symmetry Shield RP-8 and Zorbax Phenyl SDB) that were studied, the Waters Symmetry Shield RP-8 column provided a slightly higher efficiency and lower peak tailing for both analytes. The optimal mobile phase conditions were established by varying the concentration of acetonitrile, pH and flow rate. Feed samples were extracted with methanol / water (50:50 v/v) for 60 minutes. Further solid-phase clean-up on an AccuBond Alumina N cartridge was performed to obtain an extract suitable for HPLC analysis. The calibration curves showed acceptable linearity in the concentration range from 0.1 to 50 mg/L with correlation coefficients (r(2)) above 0.995. The limits of detection were 0.03 mg/L and 0.02 mg/L for carbadox and olaquindox, respectively. The mean recoveries of drugs from the feed samples spiked at 1 and 2 mg/kg were in the range of 95.3-97.2%. The applicability of this technique was demonstrated by the analysis of broiler chicken and porcine feeds.