在乳制品的生产过程中，常用季铵盐等消毒剂对生产设备等进行消毒，因此乳制品中存在季铵盐等消毒剂的污染。本文基于QuEChERS净化技术和超高效液相色谱串联质谱（UPLC-MS/MS），建立了一种测定奶粉中5种季铵盐消毒剂残留的新方法。奶粉样品先按比例加水复原成液态乳，然后经乙腈沉淀蛋白，提取液以PSA分散净化后，采用亲水色谱柱（HILIC）分离，在质谱的多反应监测（MRM）模式下测定。结果表明，5种季铵盐在0.2~50 μg/L范围内线性关系良好，其相关系数（R）均在大于0.999，奶粉样品的方法检出限（S/N=3）在4.0~14.4 μg/kg之间，样品基质的3个添加水平的平均回收率为96.5%~115%，日内精密度（n=6）在3.1%~7.5%之间，日间精密度（n=5）在4.3%~6.7%之间。实际样品检测结果表明奶粉中存在季铵盐消毒剂的残留污染情况。本方法准确灵敏，快速简便，精密度良好，适用于奶粉中以及其他类型乳制品中5种季铵盐消毒剂的分析检检测。

Quaternary ammonium compounds (QACs) were commonly used as the disinfectants to sterilize the production equipment during the production process of dairy products, which resulted in the QACs contamination in dairy products. A new method for the determination of five QACs in milk powder was established using QuEChERS purification coupled with ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Milk powder samples were dispersed into pro-rated water to obtain the liquid milk, and then precipitated by acetonitrile. The extract was analyzed in multiple-reaction monitoring (MRM) mode of MS/MS after purifying with PSA and separating with hydrophilic column (HILIC). Consequently, the five QACs showed a good linear relationship in concentration ranges of 0.2~50 μg/L, with the correlation coefficients over 0.999. This method was validated in terms of linearity, sensitivity, precision, accuracy. The limits of detections (LODs, S/N=3) for milk powder samples were in the range of ranged from4.0-14.4 μg/kg, and the recoveries were in the range of 96.5% - 115%.The relative standard deviations (RSDs) of intra-day precision and inter-day precision were 3.1-7.5% and 4.3~6.7%, which indicated that there were QACs residues in milk powder The proposed method demonstrated accuracy, sensitivity, rapidity, simplicity and good precision, which was suitable for the analysis and detection of five QACs in milk powder and other dairy products.