| An analytical method was developed for quantification of clenbuterol in ovine serum, urine, liver, muscle and hair samples using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Matrix compensation was applied to eliminate the effect of matrix after sample extraction, concentration, and solid-phase cleanup. The quantification range of the method was 5~200 ng/mL for serum and urine samples and 5~100 ng/g for liver, muscle and hair. The determination coefficient (r) was greater than 0.99. The limit of detection was 0.06ng/mL for serum and urine, 0.03ng/g for liver and muscle, and 0.1ng/g for hair. The recovery rate was 71.50%~86.25% for serum, 81.54%~113.61% for urine, 70.78%~94.20% for liver, 100.06%~117.00% for muscle and 88.54~103.12% for hair in a concentration range at 5~20ppb. The relative standard deviation was less than 17.63%, 14.23%, 3.18%, 7.28% and 8.10% for serum, urine, liver, muscle and hair respectively. The method was proved to be sensitive and accurate for CL analysis in different ovine tissues.Pharmacokinetics and residues of CL in ovine tissues were studied. Eighteen mutton sheep were used to study the residues and depletion of CL with a dosage of 50μg/kg BW for 21 days, Urine and blood samples were collected at specified time during the experiment. Liver and muscle samples were taken from three sheep after a withdrawal time of 0, 1, 2, 3, 7and 14d. The results show that the absorption of CL in mutton sheep is rapid. CL was able to be detected within 0.4h after the treatment as 0.72±0.54 ng/mL. The first peak was 23.30±18.42 ng/mL 2h after the treatment. The maximum level of CL in serum was 143.32±7.51ng/mL on day 21 during the treatment. The CL in serum declined after the final dosage with an elimination half-life (t1/2α) of 16.5h. It was 3.14±1.86 ng/mL in serum on d14 after withdrawal. There is a rapid elimination of CL in ovine urine. CL (423.50±253.72 ng/mL) was detected in urine within 2h after the administration, and presented the maximum level (2070.00±49.71 ng/mL) on day 21. The absorption of CL in mutton sheep is rapid and the elimination is slow. It is easy to accumulate in ovine tissues.Residue of CL was high in ovine liver. CL concentration was 193.33±6.61 ng/g in liver on the last day of administration. The elimination of CL was slow in liver with the t1/2αto be 1.05d. CL concentration in liver was 9.16±0.44 ng/g on day 14 after withdrawal. Residue of CL was low in ovine muscle. CL concentration was 14.65±0.64 ng/g in muscle on the last day of administration. The elimination of CL was fast in muscle with the t1/2αto be 0.66d.CL was not able to be detected (<0.1 ng/g) in muscle on day 3 after withdrawal. High residue of CL in ovine liver is a great threat to public health. And residue of CL in ovine muscle short after the withdrawl (0~2 days) also threat public health. Liver can be used to monitor and confirm the illegal use of CL in mutton sheep.Residues of CL in ovine hair were studied. Hair is an important accumulating tissue for CL. CL concentration was 6.12±0.14ng/g in white hair and 18.11±6.52 ng/g in black hair on day 4 during the treatment. CL was accumulated in hair at different rates and in different amounts. CL concentration in black hair was higher than that in white hair from day 16 of CL application to 15 day after withdrawal. The metabolism of CL was weak in hair. CL in hair kept at a high concentration on day 0~10 after withdrawal and started to decline since day 15. Hair was an ideal target for supervision of CL illegal use in live mutton sheep, and the whole hair in the back was suggested.
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