Determination of amoxicillin residues in animal tissues by solid-phase extraction and liquid chromatography with fluorescence detection

Trace levels of amoxicillin residues were determined in animal tissues by l iquid chromatography (LC) with fluorescence detection. An improved solid-ph ase extraction (SPE) procedure requiring less flammable solvent (diethyl et her) was developed for sample preparation. Muscle samples of beef, pork, ch icken, and tilapia were extracted with a phosphate buffer followed by the m odified SPE procedure for cleanup and concentration prior to the LC-fluores cence analysis. Average recoveries of fortified amoxicillin at 5, 10, and 2 0 mu g/kg ranged from 83.9 to 85.8% in beef, 86.1 to 88.1% in pork, 81.7 to 82.9% in chicken, and 92.5 to 95.4% in tilapia, Relative standard deviatio ns were <4%.