Residue Depletion Of Tilmicosin Phosphate In Broiler Tissues

Tilmicosin is derivated from tylosin and belong to macrolide livestock antibiotics. Tilmicosin can inhibit all the gram positive bacteria, parts of gram negative bacteria, mycoplasma, spirochetes, especially for actinobacillus pleuropneumoniae, pasteurella hemolytica, pasteurella multocida and livestock mycoplasma. Tilmicosin is used to treat pneumonia in livestock, mycoplasma in chickens and mastitis. Tilmicosin phosphate is obtained from tilmicosin by chemical reaction which reacts with the phosphoric acid and water. Although the effective ingredient is tilmicosin, the tilmicosin phosphate is widely used in veterinary clinic because of its highly soluble in water, special antibacterial activity and pharmacokinetic characteristics. The aim of this paper is to provide a theory evidence of the elimination regularity and residues of tilmicosin phosphate in broiler tissues by an improved HPLC method.To understand the tissue residues of tilmicosin phosphate in broiler tissue and formulate the determination of the withdrawal time, the detection method of tilmicosin in broiler was established and improved in this study by high performance liquid chromatograph (HPLC). The elimination regularity and residues of tilmicosin phosphate in broiler tissues were detected at UV 280 nm and tested by conditions of C18 column (4.6× 50 mm,5 μm), the determining mobile phase proportion of acetonitrile, tetrahydrofuran, dibutylamine phosphate buffer, water was 10:5:5:80. Broiler tissue is purified by BondElut C18 Column of solidphase extraction (SPE). The results showed that the average recovery rates of tilmicosin were between 77.02%～115.04%, and RSD were between 1.86%～ 19.19%. Chromatogram displayed peak time and peak shapes were perfect, response was well, tilmicosin was separated from the other components. The results showed the good linear relationship between the peak area and the corresponding concentration, the linear range was from 0.05 to 25.0 μg/mL (R2= 0.9998), the average recovery is above 75%. The detection limit of tilmicosin in the muscle, liver and kidney were 0.010 μg/g,0.025 μg/g, 0.025 μg/g respectively, the quantitation limit in the muscle, liver and kidney were 0.020 μg/g,0.050 μg/g,0.050 μg/g respectively. After 7 days of oral administration at dosage of 16 mg/kg, the residues of tilmicosin in liver, kidney and muscle tissues of broilers decreased significantly within 4 hours to 15 days after discontinuation. According to the MRLs and the calculation by software WT1.4, the withdrawal period of tilmicosin is 9.6, 12.8 and 13.96 days in liver, kidney and muscle respectively, suggesting that the withdrawal period of tilmicosin phosphate in broiler should be 14 days.