| The number of live pigs that exported to HongKong from Jiangxi provine ranked second in the whole country.About 400,000 live pigs from Jiangxi province were shipped and exported to HongKong,and the edible tissues of these pigs accounted for one third of the whole market share ofHong Kong.Ensuring the smooth delivery of live pigs could stabilize the prosperity of Hongkong,and safeguard the basic interests of the majority of farmers in Jiangxi.Until the end of this study,103 maxium residue limits of 19 classes of veterinary drugs were specified in "Harmful Substances in Food Regulations" of Hong Kong.In order to improve the detection efficiency of these harmful residues,and shorten release time,we made efforts on the technical difficultiesencountered in detection process,and the results are listed as bellow:First,we developed and validated aLC-MS/MS method for simultaneous determination of 37 veterinary drugs in pig urine.The urine samples were hydrolyzed by enzyme,and purified by SPE column.The target analytes were quantitatively analysed by matrix matched external standard method combined with deuterated internal standards method.The limits of detection(LOD)and the limits of quantitative(LOQ)of sulfamides(SAs)were 3.0 μg/kgand10.0 μg/kg,respectively.When the urine samples were spiked at three levels of 1,2 and 4 times of LOQ,the average recoverys ranged from60.1%to 109.0%,and the relative standard deviations(RSD)ranged from2.33%to 15.73%.The LOD and LOQ of quinolones(QNs)were determined to be 3.0 μg/kgand10.0 μg/kg,respectively.When the urine samples were spiked at three levels of 1,2 and 4 times of LOQ,the average recoverys were 75.4%～109.0%,and the relative standard deviations(RSD)were 2.37%～11.81%.The LOD and LOQof tetracycline(TCs)were 3.0 μg/kgand10.0 μg/kg,respectively.When the urine samples were spiked at three levels of 1,2 and 4 times of LOQ,the average recoverys were 60.0%～106.6%,the RSD values were 3.94%～11.85%.The LOD and LOQof lincomycinwas0.3 μg/kgand1.0 μg/kg,respectively.When the urine samples were spiked at three levels of 1,2 and 4 times of LOQ,the average recoverys were88.1%～108.0%,the RSD values were 5.87%-7.53%.The LOD and LOQof erythromycinwere 0.3μg/kgand1.0 μg/kg,respectively.When the urine samples were spiked at three levels of 1,2 and 4 times of LOQ,the average recoverys were76.7%-109.0%,RSDwere 7.39%～12.7%.The LOD and LOQof chloramphenicols(CAPs)vet drugswere 0.03μg/kg～0.3μg/kgand 0.1 pg/kg～1.0μg/kg,respectively.When the urine samples were spiked at three levels of 1,2 and 4 times of LOQ,the average recoverys were 62.6%～109.3%,the RSD values were 5.24%～18.15%.The LOD and LOQofβ-agonistswere0.3μg/kgand1.0 μg/kg,respectively.When the urine samples were spiked atAt three levels of 1,2 and 4 times of LOQ,the average recoverys were 82.7%～109.2%,the RSD values were 1.71%～10.25%.The LOD and LOQof tiamulin was 3.0 μg/kgand10.0 μg/kg,respectively.When the urine samples were spiked at three levels of 1,2 and 4 times of LOQ,the average recoverys were 81.1%～108.9%,the RSD values were 1.69%～9.20%.The purpose was implemented with the efficiency was 5 times higher than that of the traditional method and the cost of supplies reduced by 70 percent while the method could meet the regulatory requirement.Second,we established a LC-MS/MS method for simultaneous determination of 23p-agonist residuesin the pig liver and urine.The samples were hydrolyzed by enzyme and purified by SPE column.The analytes were quantitatively analysed by matrix matched external standard method coupled with deuterated internal standards method.For the urine sample,the LODof 23 compounds were 0.03μg/kg～0.3μg/kg,and theLOQwere 0.1μg/kg～1μg/kg.When the liver and urine samples were spiked at three levels of 1,2 and 10 times of LOQ,the average recoverys were 63.4%～120.0%,the RSDwere 1.8%-20.4%.For the liver sample,the LOD of 23 compounds were 0.03μg/kg～0.3μg/kg,and the LOQ were 0.1μg/kg～1μg/kg.When the liver and urine samples were spiked atthree levels of 1,2 and 10 times of LOQ,the average recoverys were 62.0%～119.9%,the RSDwere 1.8%～15.4%.The established LC-MS/MS methods involved most of β-agonists could meet the regulatory requirement and obtained satisfying results of proficiency test(PT).Third,we established aLC-MS/MS method for the determination of 5 aminoglycosides in pig liver.The samples wereextracted by the acid solutionand,and purified by MSPD coupled with SPE column.The analytes were quantitatively analysed by matrix matched external standard method.The LODwere determined to be 2.0μg/kg～30.0μg/kg,and the LOQ were 5.0μg/kg～100.0μg/kg.When the liver samples were spiked at three levels of 1,2 and 4 times of LOQ,the average recoverys were 71.6%～107.5%,the RSD values were 4.3%～11.3%.The established methods could meet the regulatory requirement andresolved the difficulty that the impact presented as the decline in the sensitivity of the negative model of the LC-MS/MS system which would occurred with the using of the ion pairing agent in the traditional method.Fourth,this study investigated the veterinary drug residue levels in 26 pig farms in Jiangxi Province during the past 1 years,involving a total of 314 samples,including 24 pig liver samples and 290 pig urine samples.The data of 17202 items of veterinary drug residuesconsisted of 672 items of pig liver and 16530 items of pig urine.It has been found that the use of banned drugs in the live pigs exported to HongKong from Jiangxi had been well controlled.The use of restricted drug is widespread,such as chlortetracycline,oxytetracycline,tetracycline,doxycycline,lincomycin,ciprofloxacin,flumequine,sulfadiazine,trimethoprim,sulfachloropyridazine and sulfamethazine etc.The species and quantity of veterinary drugs in some pig farms are consistantly above average.The inspection measures for purchased feed and other inputs are not perfect enough.The proposed methods also plays a technical support role in the two emergency detection events.In summary,we established a variety of detection methods for simultaneous determination of multiple veterinary drug residues in live pig exported to Hong Kong.These established methods are suitable for use constitute the system of detection of veterinary drug residues in Jiangxi pig tissues for Hong Kong.The difficulties encountered in practical work were solved by applied to the detection of large samplesand the result meet the expected requirements. |
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