Abstract: An ultra performance liquid chromatography-tandem mass spectrometry method for simultaneous quantitative determination of four quaternary ammonium compounds in dairy products, including milk, yogurt and milk powder, has been established. Quaternary ammonium compounds from samples were extracted with methanol and cleaned up by solid phase extraction using a weak cationic exchange reversed-phase adsorbent (WCX). The chromatographic separation was achieved using a mixture of formic acid and methanol (2:98, V/V) as the elution solvent. The eluate was evaporated to dryness under a stream of nitrogen gas and the residue was re-dissolved prior to analysis using a positive electrospray ion source in the multiple reaction monitoring mode. The limit of quantification was 10 μg/kg for dodecyl trimethyl ammonium bromide, benzylcetyldimethyl ammonium chloride, tetradecyl dimethyl benzyl ammonium chloride and didecyl dimethyl ammonium chloride in all three dairy products. The recoveries at spiked concentration levels of 10-200 μg/kg were 81.4%-105.6%, with relative standard deviations ranging from 0.97% to 6.04%. The matrix effect was in the range of 90.89%-234.94%. This method was rapid, accurate, repeatable and was suitable for the determination of quaternary ammonium compounds in various dairy products.

Key words: ultra performance liquid chromatography-tandem mass spectrometry; quaternary ammonium compounds; dairy products; solid phase extraction

摘要： 建立牛乳、酸乳和乳粉3 种基质中超高效液相色谱-串联质谱同时检测4 种季铵盐类化合物残留的检测方法。用甲醇进行提取，经混合型弱阳离子交换反相吸附剂（WCX）固相萃取柱净化，2%甲酸甲醇溶液洗脱，氮吹后复溶，采用电喷雾正离子源、多反应监测模式进行检测。结果表明：牛乳、酸乳和乳粉中十二烷基三甲基溴化铵、十六烷基二甲基苄基氯化铵、十四烷基二甲基苄基氯化胺和二癸基二甲基氯化铵的定量限均为10 μg/kg；季铵盐类化合物添加量为10～200 μg/kg时，回收率为81.4%～105.6%，相对标准偏差为0.97%～

关键词: 超高效液相色谱-串联质谱；季铵盐类化合物；乳制品；固相萃取