This article introduces the establishment of an ICP-oaTOF-MS (Orthogonal Acceleration Time-of-Flight Mass Spectrometry ) method for the determination of heavy metals, including As, Cd, Hg and Pb, in over 21 kinds of tobacco in a certain province. The samples were digested in a closed-vessel by microwave. Factors affecting the determination were studied in detail, such as sampling quantity, digestion solvent, working parameters for mass spectrometry, calibration curve, detection limit, recovery and precision tests of the method. The optimum conditions for the determination were tested and are discussed in this paper. For all of the analyzed heavy metals, the correlative coefficients of the calibration curves were over 0.9998. The recovery rates were 91.49% - 106. 25% , relative standard deviations (RSD) were lower than 2% and detection limits were 0. 093 —0. 168 μg/L. Under the given analytical conditions, the contents of the four elements of the same cultivars and stalk positions varied significantly among different locations. The contents of As, Pb, Cd and Hg had ranges of 0.503 - 1.737 mg/kg, 1.826 -4.969 mg/kg, 0.656 -2.641 mg/kg and 0.042 -0.584 mg/kg, respectively. The contents of As and Hg have some small differences, however, the contents of Pb and Cd are significantly different. Compared with other methods, this method is simple, fast and accurate with a high sensitivity. Sample contents are preferably measured in the ng/L range. Therefore, this method can be used in heavy metal detection and quality control for tobacco which is significant to be able to determine the condition of abundance or deficiency for tobacco, and identify the quality of cigarette production.%对某省5个产地21种烟叶样品用微波密闭消解,电感耦合等离子体直角加速时间飞行质谱(ICP-oaTOF-MS)测定砷、镉、汞、铅的含量.对称样量、微波消解及质谱检测参数、同位素及内标、方法准确性及可行性进行了研究,确定了最佳的实验条件.标准曲线的相关系数＞0.9998,方法回收率为91.49％～106.25％,精密度(RSD)＜2％,检出限为0.093～0.168μg/L.对在同一品种、同一部位、不同地区的烟叶样品进行测定,结果显示各地区样品中被测元素的含量存在较大差异,As为0.503～1.737mg/kg,Pb为1.826～4.969mg/kg,Cd为0.656～2.641mg/kg,Hg为0.042～0.584mg/kg;As、Hg含量差异较小,Pb、Cd含量差异较大.相比于其他分析方法,ICP-oaTOF-MS适合对浓度低至ng/L级超痕量组分的分析,具有简便快速、准确、灵敏度高、检出限低等优点,可用于烟叶重金属的检测及质量控制,对于判断烟株的丰缺情况、鉴别烟叶制品的品质具有一定的意义.
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