Highly precise and accurate isotopic analysis of small amounts of Pb using 205Pb–204Pb and 207Pb-204Pb, two double spikes
Highly precise and accurate isotopic analysis of small amounts of Pb using 205Pb–204Pb and 207Pb-204Pb, two double spikes
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DOI：
10.1039/b310294g
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发表时间：
2003-12
影响因子：
3.4
通讯作者：
T. Kuritani;Eizo Nakamura
中科院分区：
文献类型：
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作者：
T. Kuritani;Eizo Nakamura
建立了一种新的、简便、实用的热电离质谱学分析极微量铅(~lt；∼3 ng)的方法。用两种不同类型的双峰，一种是205Pb和204Pb组成的，另一种是富含207Pb和204Pb的，用来减少204Pb误差和校正质谱分析过程中的质量分馏。用该方法对NBS981样品中的1.5ngPb值进行了重复分析，208Pb值/204Pb值的外标精密度为0.02%(2σ)。与常规的207Pb204Pb单双峰双峰法测得的1.5ngPb值相比，加入205Pb204Pb双峰后，204Pb值的外精密度降低了约60%~70%。将双峰双峰法应用于天然岩石样品的同位素分析，获得了0.06%(2σ)的外精密度，即从新鲜橄榄岩中分离出1.5ngPb208Pb204Pb值为0.06%(2∼)的铅，其中铅含量低至3.2ppb。这项新技术优于以往任何一种对极少量铅进行精确和准确的同位素分析的方法，将是未来地球科学和环境科学的一个非常强大的工具。
A new, simple, and practical method has been developed for the accurate and precise isotopic analysis of extremely small amounts of Pb (<∼3 ng) by thermal ionization mass spectrometry. Two different types of double spikes, one consisting of 205Pb and 204Pb and another enriched in 207Pb and 204Pb, are used to reduce “204Pb error” and to correct mass fractionation during mass spectrometry. Using this technique, replicate analyses of 1.5 ng of Pb from NBS981 were performed, and an external precision of 0.02% (2σ) was attained for the 208Pb/204Pb ratio. Compared with results for 1.5 ng of Pb by the normal double spike method using a single 207Pb–204Pb double spike, the external precision for the isotopic ratios involving 204Pb is reduced by about 60–70%, simply by addition of the 205Pb–204Pb double spike. The two double spikes method was also applied to isotopic analyses of natural rock samples, and we obtained an external precision of 0.06% (2σ) for 208Pb/204Pb in ∼1.5 ng of Pb separated from fresh peridotite, in which the Pb concentration is as low as 3.2 ppb. This new technique is superior to any previous method for precise and accurate isotopic analyses of extremely small amounts of Pb, and will be a highly powerful tool in the future of earth science and environmental science.