| Tylosin tartrate-amoxicillin sodium compound medicine has been developed by ourselves for prevention and treatmant of Streptococcus suis infections. Tylosin is one of the agent of macrolide antibiotics, it has highly killing effect against gram-positive bacteria and gram-negative bacteria. The European Union (EU) has established a maximum residue limit (MRL) of 0.1mg/kg for tylosin in porcine edible tissues (heart, liver, lung, kidney, muscle and fat), China Ministry of Agriculture has established a MRL of 0.2 mg/kg for tylosin in 2002. Amoxicillin is one of the agent ofβ- lactam antibiotics, it has a high activity against pathogens in pigs, such as Actino-bacillus pleuropneumoniae, Streptococcus suis, Pasteurella multicoda, and Escherichia coli.The EU and China Ministry of Agriculture have established a MRLof 0.05mg/kg for amoxicillin in porcine edible tissues.In order to keep this compound medicine used standardly in hogpen, keep human body health, develop animal husbandry and promote the product import, it is necessary to establish residue monitoring system and withdrawl time.A ultra performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (UPLC/MS/MS) for determination of tylosin tartrate residues in swine edible tissues has been developed. Tissues are extracted with acetonitrile, purification by C18SPE cartridge,confirmation and quantification by mass spectrum in the multiple reaction monitoring(MRM)mode via positive electrospray ionization(+ESI), the structure was elucidated by full scan mode. The linear ranges of tylosin tartrate is between 5 ng/mL～500ng/mL,and the linear correlation coefficient is 0.9993～0.9996.The recoveries of tylosin tartrate at the spiked concentration levels of 0.05mg/kg,0.1mg/kg,0.2mg/kg ranged from72.6±4.14%～88.3±5.12%,with RSD of 4.5%～5.9%. Within day CV is 7.3%～10.1%, between day CV is 7.2%～14%.The detection limit is 5ng/g, the limit of quantitation is 15 ng/g.A UPLC/MS/MS for determination of amoxicillin residues in swine edibility tissues has been developed. Tissues are extracted with acetonitrile and water (15/2, v/v), purification by HLB SPE cartridge. The linear ranges of amoxicillin sodium is between 0.01μg/mL～1μg/mL,and the linear correlation coefficient is 0.9992～0.9995.The recoveries of amoxicillin at the spiked concentration levels of 0.025mg/kg,0.05mg/kg,0.1mg/kg ranged from 65.9±3.49%～73.2±3.95%,with RSD of 5.1%～6.5%. Within day CV is 5.8%～7.8%, between day CV is 5.1%～12.5%.The limit of detection is 0.01μg/g, the limit of quantitation is 0.03μg/g. In order to study the depletion tylosin tartrate amoxicillin sodium compound medicine residues in the porcine tissues, amoxicillin sodium-tylosin tartrate compound medicine was fed to pigs at clinical recommended dose. The results indicated that concentrations of tylosin tartrate residue were 0.27±0.03mg/kg in liver,0.23±0.05 mg/kg in kidney after withdrawal for 12h, the concentrations of tylosin tartrate residue were 0.11±0.03 mg/kg in liver,0.06±0.04 mg/kg in kidney,0.05±0.01 mg/kg in lung,0.05±0.03 mg/kg in heart after withdrawal for 36h, after withdrawal for 60h, the concentrations of tylosin tartrate residue were 0.04±0.02 mg/kg in liver,0.02±0.01 mg/kg in lung, they are lower than MRLs;After withdrawal for 12h, the concentrations of amoxicillin residue were 0.20±0.05mg/kg in liver,0.18±0.05 mg/kg in kidney, the concentrations of amoxicillin residue were 0.02±0.01 mg/kg in liver after withdrawal for 60h, it is lower than MRL. According to the usual methods of calculation for the withdrawal time in our country, the withdrawal time for this compound medicine was advised as 60h in pig.
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