Determination Of Erythromycin Residues In Edible Tissues Of Cattle And Sheep By LC-MS/MS

Erythromycin(ERM)is a fourteen-membered ring macrolide antibiotic(Molecular Formula C37H67NO13)extracted from the culture solution of Streptomyces erythromycin.It has a wide range of applications in veterinary medicine,mainly for mild to moderate infections caused by penicillin-resistant Staphylococcus aureus and cases allergic to penicillin,such as mastitis and Pig erysipelas and so on.It also has a good effect on chronic respiratory diseases of poultry,infectious rhinitis and porcine mycoplasmal pneumonia.The veterinary drug is incorrectly used in the animal feeding process and in the veterinary clinic,and the erythromycin residue in the animal can be caused by not complying with the drug withdrawal period and the like.The aim of this study was to establish a method for the determination of erythromycin residues in edible tissues of cattle and sheep by LC-MS/MS in order to provide a basis for the detection of erythromycin residues in edible tissues of cattle and sheep.The research contents:1.Establish a method for detecting erythromycin residues in edible tissues of cattle and sheep by LC-MS/MS.The best pretreatment method for the muscle,liver,kidney,lung,intestine and milk and goat milk of cattle and sheep was compared.The final tissue samples were extracted with acetonitrile,repeated degreasing with n-hexane,pre-treatment with low temperature centrifugation,and pre-treatment with dairy products using QuEChERS.Using CAPCELL PAK(4.6 mm× 150 mm,5 ?m)column,30? column temperature,injection volume 5 ?L,acetonitrile:ammonia water(V/V=92:8),tissue sample flow rate of 0.5 mL/min,dairy products 0.8 The flow rate of mL/min was isocratic.Electrospray ionization source(ESI),multiple reaction monitoring mode under positive ion scanning.2.According to the polarity of the drug and the nature of the sample,the extractant was selected from acetonitrile,chloroform and formic acid respectively;the different volumes of the extractant acetonitrile and the degreaser n-hexane were selected;the mobile phase was based on erythromycin and Rhodotor The characteristics of the element and the mass spectrum were selected from three kinds of ammonium formate,ammonium acetate and ammonia;the different concentrations of ammonia were compared with 1.5%,0.5%and 0.2%;compared with Supersil ODS-B and CAPCELL PAK MGII-C18,Poroshell 120EC-C18 three columns;compared 5 different column temperatures of 20? C,25 ?,30?,35 0 C and 40?;compared the elution conditions of isocratic elution and gradient elution.The results showed that the best extractant was 20 mL of acetonitrile,the degreaser was 20 mL of n-hexane,the mobile phase was acetonitrile-0.5%ammonia(92:8),the column was CAPCELL PAK MGII-C18,and the column temperature was 30?.The tissue sample was eluted with a flow rate of 0.5 mL/min and a flow rate of 0.8 mL/min of the dairy product.Erythromycin has a good linear relationship in the range of 5 ng/mL to 200 ng/mL,and R2 reaches 0.99.The detection limit of this method is 5?g/kg,the limit of quantification is 20 ?g/kg,the relative recovery is 77%-120%,and the precision is good(the relative standard deviation between day and day is less than 10%).The RSD of edible tissue samples of cattle and sheep at 4 ?,room temperature and-20?C for one week was less than 10%,and the stability was good.The results of the specific investigation showed that the retention time of erythromycin and roxithromycin(internal standard)in tissue samples was 5.967min and 8.548min respectively;the retention time of dairy products was 3.608min and 4.946min respectively.The peak shape is good and there is no interference between the peaks.Conclusion:The determination of erythromycin residues in edible tissues of cattle and sheep by this method is in line with the requirements of the Ministry of Agriculture Bulletin No.235 on the maximum residue limit of erythromycin in cattle,sheep and milk.It has high accuracy,good stability and strong specificity.It is expected to be certified as a standard test method after laboratory verification.