Determination of macrolide antibiotics in porcine and bovine urine by high-performance liquid chromatography coupled to coulometric detection

A high-performance liquid chromatography method coupled to coulometric detection has been applied for the determination, in a single run, of up to eight macrolide antibiotics ( erythromycin [ERY], tylosin [TYL], tilmicosin [TILM], spiramycin 2 [SPI 2], spiramycin 3 [ SPI 3], josamycin [ JOS], kitasamycin [ KIT], and rosamicin [ ROS]) in spiked porcine and bovine urine. Quanti. cation was performed using matrix-matched calibration with roxithromycin (ROX) as the internal standard. The detection limits for each drug were below 3.5 ng injected ( equivalent to an initial concentration below 0.07 mg L-1) for porcine urine and below 5 ng injected ( equivalent to an initial concentration below 0.10 mg L-1) for bovine urine. Recoveries from urine samples spiked at three different concentrations within the linear range were not significantly dependent on concentration. The entire procedure provides average macrolide recoveries ranging from 69.7 to 96.6% for bovine urine and from 75.5 and 96.1% for porcine urine.