Elimination regularity and residues of tilmicosin phosphate in broiler tissues

The elimination regularity and residues of tilmicosin phosphate in broiler tissues were detected at UV 280 nm by using improved high performance liquid chromatography(HPLC),with the proportion of acetonitrile,tetrahydrofuran,dibutylamine phosphate buffer and water was 10∶5∶5∶80 by the mobile phase.The results showed that the average recovery rates of tilmicosin were 77.02%-115.04% and the detection limit of tilmicosin in muscle,liver and kidney were 0.010,0.025 and 0.025 μg·g-1,respectively.The quantitation limits in muscle,liver and kidney were 0.020,0.050 and 0.050 μg·g-1,respectively.After 7 days of oral administration at dosage of 16 mg·kg-1,the tilmicosin residues in liver,kidney and muscle tissues of broiler decreased significantly within 4 hours to 1 day after discontinuation.The highest level of tilmicosin residues occurred in liver and followed by kidney and the lowest in muscle tissues.According to the calculation by software WT 1.4,the withdrawal period of tilmicosin was 9.6,12.8 and 13.96 days in liver,kidney and muscle respectively,suggesting that the withdrawal period of tilmicosin phosphate for broiler using should be 14 days by the 95% confidence interval analysis.