Determination of Ce isotopes by TIMS and MC-ICPMS and initiation of a new, homogeneous Ce isotopic reference material
Determination of Ce isotopes by TIMS and MC-ICPMS and initiation of a new, homogeneous Ce isotopic reference material
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DOI：
10.1039/b705306a
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发表时间：
2007-10
影响因子：
3.4
通讯作者：
M. Willbold
中科院分区：
文献类型：
--
作者：
M. Willbold
放射成因138 Ce/136 Ce比值在地质和宇宙学物质中是一种有价值的示踪和定年工具。然而，全球138 Ce/136 Ce比率的变化很小（例如，0.03%的洋岛玄武岩）。此外，还讨论了138 Ba的等压干扰和占主导地位的140 Ce离子束（88.5%）对138 Ce（约. 0.251%）存在分析挑战。目前采用的方法一般不考虑140 Ce低质量峰尾对138 Ce/136 Ce比值测定精度的影响。因此，报告的重现性范围仅为0.05 - 0.004%（2 RSD）。本研究采用TIMS和MC-ICPMS测定标准物质中的138 Ce/136 Ce比值。结果表明，只有通过TIMS测量Ce作为氧化物物种，结合对所获得的离子强度之间的背景的准确监测和校正，才能产生准确且可再现的138 Ce/136 C比率。与报道的方法相比，该方法的重现性提高了两倍以上（0.002%; 2 RSD）。单个误差源的识别和定量导致该方法的合并标准不确定度为0.002%（2 RSE）。CeO 2参考材料JMC 304的已发表数据的比较揭示了其同位素异质性。因此，我们用艾姆斯实验室的超纯金属铈制备了一种新的标准物质。现在可供分发。新参比物质的初始表征得到138 Ce/136 C比值为1.33738 ± 0.000005（2σ平均值; N = 35）作为工作值。
Radiogenic 138Ce/136Ce ratios in geological and cosmological materials are a valuable tracer and dating tool in geo- and cosmochemistry. However, the variation in global 138Ce/136Ce ratios is small (e.g., 0.03% in ocean island basalts). In addition, the isobaric interference of 138Ba and the influence of the dominant 140Ce ion beam (88.5%) on 138Ce (ca. 0.251%) during mass spectrometric analysis present an analytical challenge. Hitherto employed methods generally dismiss the influence of the 140Ce low-mass peak-tail on the accuracy of the determined 138Ce/136Ce ratios. Therefore, the reported reproducibility ranges only from 0.05 to 0.004% (2RSD). In this study, TIMS and MC-ICPMS are used to determine 138Ce/136Ce ratios in reference materials. The results show that only the measurement of Ce as an oxide species by TIMS, combined with the accurate monitoring and correction of the background between the acquired ion intensities, can yield accurate and reproducible 138Ce/136C ratios. This method achieves a more than two-fold improvement in reproducibility (0.002%; 2RSD) compared to reported methods. The identification and quantification of individual sources of error resulted in a combined standard uncertainty of 0.002% (2RSE) for the method. A comparison of published data for the CeO2 reference material JMC 304 reveals its isotopic heterogeneity. Therefore, a new reference material has been prepared from ultra-pure Ce metal from Ames Laboratory. It is now available for distribution. An initial characterization of the new reference material yielded a 138Ce/136C ratio of 1.33738 ± 0.000005 (2σmean; N = 35) as a working value.