Abstract: A method for the simultaneous determination of Pb, Cr and Hg in milk was developed by microwave digestion combined with inductively coupled plasma mass spectrometry (ICP-MS). The sample preparation procedure, the ICP-MS parameters, the internal standard and the monitor isotope were optimized. The results showed that the digestion temperature was 180 ℃. A mixed solution of 10 μg/L 72Ge and 209Bi was selected as the internal standard to eliminate the matrix effect, and 200 μg/L Au was added to the solution to eliminate the memory effect of Hg. 208Pb, 52Cr and 202Hg were monitored with ICP-MS to determine Pb, Cr and Hg, respectively. Under the optimal conditions, detection limits of 5.0 (Pb), 1.0 (Cr) and 0.5 (Hg) μg/kg were obtained. The contents of Pb, Cr and Hg in 40 batches of commercial milk were low. The detection values were smaller than 0.011 mg/kg for Pb and smaller than 0.031 mg/kg for Cr. Only 1 sample was found to contain Hg, and the detection value was 0.008 mg/kg.

Key words: microwave digestion; inductively coupled plasma mass spectrometry (ICP-MS); Pb; Cr; Hg; milk

摘要： 针对牛乳这类特殊的食品,建立微波消解-电感耦合等离子体质谱(inductively coupled plasma mass spectrometry,ICP-MS)同时测定样品中Pb、Cr和Hg含量的方法.对样品前处理方法、ICP-MS检测条件、内标及ICP-MS监测同位素进行研究,在此基础上验证检测方法的准确度和精密度.结果表明:采用微波消解进行样品前处理,消解温度180℃即可保证样品消解完全;选择10 μg/L的72Ge和209Bi混合溶液作为待测元素Pb、Cr和Hg的内标液以消除基体效应,同时在内标液中加入200 μg/L的Au,以消除Hg的记忆效应.选择在碰撞反应模式下,分别用ICP-MS监测208pb、52Cr和202Hg来测定Pb、Cr和Hg的含量.优化后,方法的检出限分别为5.0 (Pb)、1.0 (Cr)和0.5 (Hg) μg/kg.对市面代售的40个批次的牛乳样品检测结果表明:牛乳中Pb、Cr和Hg的含量均较低,Pb的检出数值均小于0.011 mg/kg,Cr的检出数值均小于0.031 mg/kg,Hg仅有1个样品检出,且只有0.008 mg/kg.

关键词: 微波消解；电感耦合等离子体质谱；Pb；Cr；Hg；牛乳