液质联用法测定牛奶中5种β-内酰胺类抗生素

Determination of five β-lactam antibiotics in milk by liquid chromatography-mass spectrometry

[目的]建立采用LC—MS—MS分析牛奶中阿莫西林、氨苄西林、氯唑西林、苯唑西林和青霉素-G残留量的方法。[方法]牛奶样品中加入内标青霉素-D7，经乙腈沉淀后，离心并吸取上清液。上清液吹干后，通过固相萃取柱净化，然后进行检测。在液相色谱分离系统中，通过Atlantis C18柱，采用0．1％甲酸水溶液与乙腈不同比例混合的梯度流动相，根据以上各成分的不同质量数的碎片离子的强度，将5种抗生素分离并测定。[结果]在2—20μg／L范围内，与内标的峰面积比有良好的线性关系。相关系数（R。）为0．9943—0．9981，在5、10μg／L水平的标准加入回收率为88％-127％。阿莫西林、氨苄西林、青霉素、氯唑西林、苯唑西林的最低检测限量分别为5、2、2、4、4μg／L（以信噪比为10：1）。[结论]该方法利用液-液萃取和固相萃取相结合的方法，并加入同位素内标，有效地去除干扰因素，为该类抗生素的测定提供了可靠、实用的测定方法。

[ Objective] To develope a high performance liquid chromatography coupled mass spectrometry method based on C18 solid - phase extraction for simultaneous determination of five β - lactam antibiotics （ amoxicillin, ampicillin, oxacillin, cloxacillin and penicillin G） in bovine milk. [ Methods ] The samples were cleaned up with C18 SPE catridge, the extracts were analyzed by liquid chromatography- electrosprapy ionization tandem mass spectrometry （ LC - MS/MS ） in the positive mode using a isotope - labeled internal standard. [ Results ] The method was validated at the 5 and 10 μg/L level for these compounds in milk, and the limit of quantification was 5, 2,2,4,4 μg/L for amoxicillin, ampicillin , penicillin G, cloxacillin and oxacillin, and the detection range was from 2 to 20 μg/L. [ Conclusion] Liquid - liquid extraction and solid - phase extraction are combined to eliminate the interfering substance while the internal standard is used. Hence this method is adoptable for the determination of five kinds of antibiotics.