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首页> 外文期刊>Journal of Analytical Atomic Spectrometry >Determination of uranium isotope ratios by multi-static MIC-ICP-MS: method and implementation for precise U- and Th-series isotope measurements
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Determination of uranium isotope ratios by multi-static MIC-ICP-MS: method and implementation for precise U- and Th-series isotope measurements

机译：通过多静态MIC-ICP-MS测定铀同位素比：精确测量U系列和Th系列同位素的方法和实现

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摘要

In order to improve and extend the application of U- and Th-series isotope measurements a new technique for MIC-ICP-MS (multiple ion counting inductively coupled plasma mass spectrometry) was developed. This method uses either two ( double MIC) or three ( triple MIC) multipliers to measure in static mode in turn the U-isotopes U-233, U-234, U-235 and U-236. For online internal standardization, mass bias correction and cross calibration of the multipliers a U-233/U-236 double spike was used. Applying this method the level of parts per thousand% 2 sigma internal precision is reached in less than 30 min, consuming less than 5 ng of total U. The multi-static MIC-ICP-MS method improves the precision by a factor of 5 for U isotope measurement compared with TIMS and by a factor of 2 compared with published ICP-MS methods. Repeated measurements of uranium CRM-145 (otherwise NBL 112A) were performed to test the reproducibility and accuracy of the method. An average U-234/U-238 value of (5.285 84 +/- 0.000 87) x 10(-5) or a delta(234)U value of -36.96 +/- 0.16, respectively, was determined for CRM-145 in good agreement with reference data. Based on the precisely determined U isotope ratios we furthermore developed a combined multi-static U- and Th-measurement method. This approach extends this new MIC-ICP-MS technique to those U- and Th-series isotope systems having no constant isotope ratio for normalization (e.g., Th-230/Th-232, Th-230/Th-229) and is the key for new approaches to determining Ra-226/Ra-228 and Pa-231/Pa-233. The applicability of the methods presented here is demonstrated by accurate dating of very young corals (10-350 y).
机译：为了改善和扩展U系列和Th系列同位素测量的应用，开发了一种新的MIC-ICP-MS技术（多离子计数感应耦合等离子体质谱法）。该方法使用两个（双MIC）或三个（三重MIC）乘法器以静态模式依次测量U同位素U-233，U-234，U-235和U-236。对于在线内部标准化，乘数的质量偏差校正和交叉校准，使用U-233 / U-236双尖峰。采用这种方法，在不到30分钟的时间内即可达到千分之2 sigma内部精度的零件水平，消耗的总U量不到5 ng。多静态MIC-ICP-MS方法将精度提高了5倍。与TIMS相比，U同位素的测量结果与已发布的ICP-MS方法相比，其U同位素的测量结果为2。进行了铀CRM-145（否则NBL 112A）的重复测量以测试该方法的可重复性和准确性。对于CRM-145，分别确定了平均U-234 / U-238值为（5.285 84 +/- 0.000 87）x 10（-5）或delta（234）U值为-36.96 +/- 0.16与参考数据高度吻合。基于精确确定的U同位素比，我们还开发了一种组合的多静态U和Th测量方法。这种方法将这一新的MIC-ICP-MS技术扩展到了没有恒定同位素比率进行标准化的U系列和Th系列同位素系统（例如Th-230 / Th-232，Th-230 / Th-229），并且确定Ra-226 / Ra-228和Pa-231 / Pa-233的新方法的关键。此处介绍的方法的适用性通过对非常年轻的珊瑚（10-350 y）的准确年代证明。

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