A New Method And Pretreatment Materials For Detection Of Tetracycline Antibiotics And Their Epimorphous Isomers By UPLC-MS/MS

Objective: Tetracycline antibiotics(TCs)is a class of antibiotics produced or semi-synthetic from the genus actinomyces.It is effective against Gram-positive and Gram-negative bacteria and spirochaeta,leptospira,chlamydia,Rickettsia,etc.It also has obvious growth promotion and disease prevention effect on livestock and poultry such as pig,cow,chicken and duck.Therefore,TCs is widely used in clinical medicine and animal husbandry industry with excellent antibacterial action and relatively low price.However,TCs are very prone to differential isomerization,and its products are more toxic.Long-term chronic ingestion of TCs and their differential isomers will lead to the generation of drug-resistant strains,gastrointestinal dysfunction and even huge damage to liver and kidney tissues,which will cause inestimable damage to human health.Therefore,it is of great significance to establish a sensitive and accurate analytical method for the detection of TCs and their differential isomers in animal-derived food.Methods: Using pl C-MS /MS as testing instrument,Dispersive solid phase extraction(DSPE)pretreatment method is combined with methanesulfonic acid modified mobile phase to separate TCs and their differential isomers and improve the peak broadening of TCs.The key factors such as flow rate,column temperature,adsorption and desorption time,p H value,analytical solvent were optimized to establish a complete set of highly sensitive and accurate methods for the detection of TCs and their differential isomers in animal-derived foods.Results: Under the optimal UPLC-MS/MS conditions,the calibration curves of the eight TCs showed a good linear relationship(r > 0.9990)in the concentration range of μg/kg,and the detection limits were 0.023～1.760μg/kg.For DSPE,the P-CDP dosage was 35 mg,the adsorption time was 5 min,the desorption time was 5min,and the p H was 5.0.The recoveries were 85.47%-111.16%.P-CDP can be reused for more than 7 times.Conclusion: In this study,a simple,efficient and sensitive UPLC-MS/MS method was developed for the detection of residues of 8 tetracycline antibiotics(including 3 common differential isomerization products)in animal-derived foods.Methanesulfonic acid was used as the mobile phase modification agent to solve the problems of poor separation and peak widening of tetracycline antibiotics on liquid chromatography.It provides a new method for the determination of tetracycline antibiotics by liquid chromatography and mass spectrometry.Combined with the detection of practical samples by DSPE,the feasibility of this method in practical work has been proved.It has the advantages of simple operation,fast,good selectivity,high recovery rate,no buffer solution,etc.,and has broad application prospect.