Determination of uranium isotope ratios by multi-static MIC-ICP-MS: method and implementation for precise U- and Th-series isotope measurements
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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DOI：
10.1039/b415958f
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发表时间：
2005-01-01
影响因子：
3.4
通讯作者：
Dullo, C
中科院分区：
文献类型：
--
作者：
Fietzke, J;Liebetrau, V;Dullo, C
为了改进和扩展铀和钍系列同位素测量的应用，提出了多离子计数电感耦合等离子体质谱（MIC-ICP-MS）新技术。该方法使用两个（双MIC）或三个（三MIC）乘法器在静态模式下依次测量u -同位素U-233、U-234、U-235和U-236。对于在线内部标准化，使用U-233/U-236双尖峰对乘法器进行质量偏差校正和交叉校准。应用该方法，在不到30分钟的时间内达到千分之一% 2 σ的内部精度水平，消耗的总U小于5 ng。与TIMS相比，多静态MIC-ICP-MS方法的U同位素测量精度提高了5倍，与已发表的ICP-MS方法相比，提高了2倍。对铀cr -145（或NBL 112A）进行了重复测量，以测试该方法的再现性和准确性。cr -145的平均U-234/U-238值为（5.285 84 +/- 0.000 87）× 10(-5), δ (234)U值为-36.96 +/- 0.16，与参考数据吻合良好。在精确测定铀同位素比值的基础上，我们进一步开发了一种多静态U和th联合测量方法。该方法将这种新的MIC-ICP-MS技术扩展到那些没有固定同位素比值的U系列和th系列同位素系统（例如，Th-230/Th-232, Th-230/Th-229），并且是确定Ra-226/Ra-228和Pa-231/Pa-233新方法的关键。这里提出的方法的适用性通过非常年轻的珊瑚（10-350年）的准确测年证明。
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).