Simultaneous determination of five quinoxaline-1,4-dioxides in animal feeds using ultrasonic solvent extraction and high-performance liquid chromatography

An HPLC method with UV detection has been established for the simultaneous quantitative determination of five quinoxaline-1,4-dioxides (carbadox, olaquindox, cyadox, mequindox, quinocetone) in porcine, chicken and fish feeds. Feed samples were extracted with methanol/acetonitrile/water (35:35:30, v/v/v) in an ultrasonic bath, and purified by solid phase extraction (SPE) on Alumina N cartridges. The samples were analyzed on an Eclipse XDB C18 liquid chromatography column using a gradient program with methanol and water. Except for cyadox (>75%), recoveries of the drugs from feed samples spiked at 5, 50 and 200 mg kg−1 ranged from 92 to 104%. Coefficients of variation were 2–13%. The decision limits (CCα) for the five compounds were <0.45 mg kg−1, and the detection capability (CCβ) were <0.75 mg kg−1. Eight commercial feed samples have been analyzed using this method, and olaquindox was detected in three out of the eight samples. The rapid and simple method could be used for the determination of multi-residue of quinoxaline-1,4-dioxides in feed and other cereal samples at wide contamination levels (1–200 mg kg−1).