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本工作研究了采用同位素稀释火花源质谱法定值测定茶叶中Th、Pb等九种微量元素的分析方法。本方法具有灵敏度高、多元素同时测定能力强以及无需标样即可进行定量测定等特点。工作中对样品的灰化方法、谱线干扰及测量线对和最佳稀释条件的选择进行了研究。采用长寿命放射性同位素~(280)Th作为Th的稀释剂,大为提高了0.1ppm数量级Th含量的测量准确度。最后采用本方法为中科院生态环境研究中心研制的茶叶和茶树叶标样中九个微量元素提供了定值分析数据,本方法测定值与标样标准值相符情况良好,18个数据的平均差为5%。
This work studied the determination of Th, Pb and other nine trace elements in tea by isotope dilution spark mass spectrometry. The method has the characteristics of high sensitivity, simultaneous determination of multiple elements, and quantitative determination without a standard sample. Work on the sample ashing methods, spectral interference and measurement of pairs and optimal dilution conditions were studied. Using long-lived radioisotope ~ (280) Th as a diluent for Th significantly improves the measurement accuracy of Th content on the order of 0.1 ppm. Finally, this method provides the value analysis data for nine trace elements in tea and tea leaf samples developed by the Research Center for Eco-Environmental Sciences of the Chinese Academy of Sciences. The measured values of this method are in good agreement with the standard values of the standard samples. The average difference of the 18 data is 5%.