Stability of thirteen antimicrobials in incurred samples of animal tissues, milk, eggs, and honey after freeze-storage

Monitoring of antimicrobials residues in food of animal origin is performed by control laboratories to ensure public health, and knowledge of the stability of antimicrobials during storage is essential for the reliability of results. For stability studies, analysis of incurred samples is preferential to fortified samples due to the possible conversion of antimicrobial metabolites back to parent compounds during sample preparation, storage, and analysis of the incurred samples, resulting in an increased concentration of the analyte. We have analyzed the concentrations of 13 antimicrobials from 8 groups (tetracyclines, fluoroquinolones, phenicols, sulfonamides, aminoglycosides, penicillins, macrolides, and nitroimidazoles) at different time points of freeze-storage (1 week; 1, 2, and 3 months) using HPLC-MS/MS. Incurred samples were prepared from muscle tissue, liver, kidneys, eggs, and milk taken from different animals (cows, pigs, poultry, goats, and fish). Incurred and fortified samples of honey were investigated as well. The results have shown that all analytes in all samples were stable during the investigated periods regardless of animal species, matrix, and concentration levels.

为保障公众健康，监管实验室需对动物源食品中的抗菌药物残留开展监测；而掌握抗菌药物在储存过程中的稳定性，对检测结果的可靠性至关重要。在稳定性研究中，天然污染样品（incurred samples）的检测优先于加标样品（fortified samples），这是因为在天然污染样品的前处理、储存及检测环节中，抗菌药物代谢物可能逆向转化为母药，进而导致待测物浓度升高。本研究采用高效液相色谱-串联质谱（HPLC-MS/MS），对8大类共13种抗菌药物在冷冻储存的不同时间点（1周、1、2及3个月）的浓度进行了检测。上述8大类抗菌药物分别为四环素类、氟喹诺酮类、苯丙醇类、磺胺类、氨基糖苷类、青霉素类、大环内酯类及硝基咪唑类。天然污染样品取自牛、猪、家禽、山羊及鱼类等不同动物的肌肉组织、肝脏、肾脏、鸡蛋与乳汁并完成制备。此外，本研究还对蜂蜜的天然污染样品与加标样品进行了考察。结果显示，在所考察的储存周期内，所有样品中的所有待测物均保持稳定，且不受动物种类、样品基质及浓度水平的影响。