Abstract: The concentrations of tilmicosin residues in swine excreta were determined by HPLC. Swine excreta were extracted with acetonitrile and 0.1mol·L-1 potassium dihydrogen phosphate buffer (pH 2.5). The extracts were applied to C18 solid-phase extraction (SPE) cartridge. The residue was eluted from SPE cartridge with methanol-acetonitrile-ammonium acetate (20:80:0.77, v:v:g), and the eluate was determined by HPLC at 290 nm. Recoveries of tilmicosin in urine fortified at 0.025?g·ml-1-2.0?g·m;-1 and in faeces fortified at 0.05?g·g-1-5.0?g·g-1 were in the range of 83.4%-95.7% and 58.8%-73.9%, respectively. Coefficients of variation were in the range of 6.6%-8.9% and 8.7%-12.4%, respectively. The limits of quantification (LOQ) were 0.025?g·ml-1 and 0.05?g·g-1 for tilmicosin in urine and faeces, respectively. The limits of detection (LOD) were 0.0125?g·ml-1 and 0.025?g·g-1 for tilmicosin in urine and faeces, respectively. The method complied with the requirement for tilmicosin correlative study.

Key words: Tilmicosin, Swine excreta, High performance liquid chromatography, Residue determination