固相萃取-高效液相色谱-串联质谱法同时测定牛奶中多种季铵类化合物残留

摘要

A method was proposed for the determination of the residues of the quaternary ammonium compounds ( QACs) in milk by solid phase extraction-high performance liquid chromatography-tandem mass spectrometry ( HPLC-MS/MS ) . The sample was extracted with acetonitrile, cleaned-up by weak cationic exchange solid phase extraction cartridge and concentrated in a gentle nitrogen stream. The separation of 5 QACs was performed on a Thermo C18 column (150 mmí2. 1 mm, 3 μm) using gradient elution of 0. 1%acetic acid and 20 mmol/L ammonium acetate methanol as the mobile phase within 7 min. The QACs were analyzed under the multiple reaction monitoring ( MRM ) mode with positive electrospray ionization. The calibration curves were linear well with correlation coefficient over 0 . 99 . The limit of quantification of the method was 1 . 0 μg/kg for hexadecyltrimethyl ammonium bromide and 0 . 2 μg/kg for benzyldodecyldimethyl ammonium bromide, tetradecyl trimethyl ammonium bromide, benzyldimethyltetradecyl ammonium chloride and didecyldimethyl ammonium bromide. The average recoveries for 5 QACs were between 70. 5% and 96. 6% in pure milk, between 69. 1% and 87. 9% in fresh milk and between 67. 1% and 93. 3% in low fat milk at the spiked levels of 2, 10 and 20 μg/kg, with relative standard derivation ( RSD) from 1. 4% to 11. 6%. The developed method is simple and sensitive, and suitable for rapid analysis of quaternary ammonium compounds in the milk.%建立了快速测定牛奶中季铵类化合物多残留的固相萃取-高效液相色谱-串联质谱法。以乙腈提取目标化合物,弱阳离子固相萃取柱萃取净化,氮吹浓缩处理,C18色谱柱分离,0.1%乙酸-20 mmol/L乙酸铵甲醇溶液梯度洗脱,多反应监测正离子模式扫描。目标化合物在7 min内实现良好分离,并在各自相应浓度范围内线性良好,相关系数>0.99,方法的定量限：十二烷基二甲基苄基溴化铵、十四烷基三甲基溴化铵、十四烷基二甲基苄基氯化铵和双十烷基二甲基溴化铵为0.2μg/kg；十六烷基三甲基溴化铵为1.0μg/kg。在2.0,10和20μg/kg添加浓度,目标化合物在纯牛奶、鲜牛奶和低脂牛奶中的平均回收率分别为70.5%~96.6%,69.1%~87.9%和67.1%~93.3%,相对标准偏差为1.4%~11.6%。本方法操作简便,灵敏度高,适用于牛奶中季铵类化合物多残留的快速检测。