Determination of Antibiotics Residues in Milk Using a QuEChERS Method Using Full Factorial Design and Liquid Chromatography-Tandem Mass Spectrometry

This study evaluated different methods of extraction based on quick, easy, cheap, effective, rugged and safe (QuEChERS) method for analysis of the antibiotics ceftiofur, cloxacillin and enrofloxacin in milk using ultra-performance liquid chromatography-tandem mass spectrometry. The QuEChERS acetate method has been shown to be inefficient for extracting such antibiotics. The optimized QuEChERS method presented excellent recoveries, from 95 to 99%. A complete factorial design was used to evaluate the effects of variables of the clean-up step: anhydrous octadecylsilane (C18), primary secondary amine (PSA) and sodium acetate (NaAc). Linearity (R2) above 0.96 was achieved for all compounds. Accuracy and precision were assessed by recovery. Accuracy was 91-99%. Intraday precision with relative standard deviations (RSD) lower than 12.3% and interday precision lower than 12.4% were obtained. Limits of detection (LOD) and quantification (LOQ) were obtained between 1.4-6.8 and 1.5-8.7 µg L-1, respectively. The applicability was evaluated using 91 real milk samples.本研究以快速、简便、廉价、高效、稳定且安全（QuEChERS）前处理方法为基础，评估了不同萃取方案，旨在通过超高效液相色谱-串联质谱（ultra-performance liquid chromatography-tandem mass spectrometry）分析牛奶中的头孢噻呋（ceftiofur）、氯唑西林（cloxacillin）与恩诺沙星（enrofloxacin）三种抗生素。研究表明，乙酸盐型QuEChERS方法对上述抗生素的萃取效率欠佳。经优化后的QuEChERS方法回收率优异，可达95%~99%。本研究采用完整析因设计，对净化步骤中的三个变量——无水十八烷基硅烷（C18）、伯仲胺吸附剂（PSA）与乙酸钠（NaAc）的影响进行了评估。所有目标化合物的线性相关系数（R²）均大于0.96。本研究通过回收率评价方法的准确度与精密度，其准确度区间为91%~99%；日内精密度的相对标准偏差（RSD）低于12.3%，日间精密度低于12.4%。方法的检出限（LOD）与定量限（LOQ）分别为1.4~6.8 µg·L⁻¹与1.5~8.7 µg·L⁻¹。本研究利用91份实际牛奶样本评估了该方法的适用性。