Improved in-situ Determination of Sr Isotope Ratio in Silicate Samples Using LA-MC-ICP-MS and its Wider Application for Fused Rock Powder
Improved in-situ Determination of Sr Isotope Ratio in Silicate Samples Using LA-MC-ICP-MS and its Wider Application for Fused Rock Powder
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改进的 LA-MC-ICP-MS 硅酸盐样品中 Sr 同位素比的原位测定及其在熔岩粉中的更广泛应用
DOI：
10.1007/s12583-019-1214-0
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发表时间：
2020
影响因子：
3.3
通讯作者：
Shaoyong Jiang
中科院分区：
文献类型：
--
作者：
Lüyun Zhu;Ganglan Zhang;Yongsheng Liu;Jie Lin;Xirun Tong;Shaoyong Jiang
固体样品Sr同位素原位测定具有空间分辨率高、制样方便、快速等优点。然而，由于缺乏从Sr中分离基质元素的柱化学方法，干扰校正（特别是87Rb对87Sr的等压干扰）成为高精度原位Sr同位素分析结果的一大难题。在本研究中，我们系统地评估了等压干扰的影响，并采用了一种改进的Rb等压干扰校正策略。具体来说，作为数据校准的外部标准，内部硅酸盐标准（Rb-std）由纯氧化物粉末熔融而成。新标准（Rb-std）在测定Rb （βRb）的质量分馏因子时，Sr （<1 ppm）、Yb （<0.09 ppm）和Er （<0.05 ppm）的含量极低，直接避免了双荷离子和等压干扰的麻烦。与以往采用高Rb （30.07 ppm）、Sr （482 ppm）、Yb （1.13 ppm）和Er （1.18 ppm）的外部标准物质sth06 /80- g计算质量分馏相比，改进后的方法能提供更准确的数据。然后，将这些来自Rb-std的βRb线性插值到未知样品上，对87Sr上的87Rb进行校正。对BIR-1G、BCR-2G、BHVO-2G、T1-G和athog系列国际标准物质的分析结果表明，改进后的方法提高了原位测定Sr同位素Rb/Sr的上限，减小了结果的相对标准偏差。Rb/Sr上限（<0.33）的改进不仅将扩大硅酸盐矿物微量分析的范围，而且将结合快速聚变技术扩大火山岩整体Sr同位素测定的范围。
The in-situ Sr isotope determination of solid samples has the advantages of high spatial resolution and convenient and rapid sample preparation. However, due to the lack of column chemistry separation of matrix elements from Sr, the interference correction (especially the isobaric interference from 87Rb on 87Sr) becomes a big issue for high precise in-situ Sr isotope analytical results. In this study, we evaluated the influence of isobaric interference systematically and adopted an improved strategy for isobaric interference correction of Rb. Specifically, as an external standard for data calibration, an in-house silicate standard (Rb-std) was fused from pure oxide powders. The new standard (Rb-std) shows very low contents of Sr (<1 ppm), Yb (<0.09 ppm) and Er (<0.05 ppm), which directly avoid the trouble of interference of doubly charged ions and isobar, when we determinate the mass fractionation factors of Rb (βRb). Our improved method can provide more accurate data than previous researches, in which the mass fractionation were calculated from an external reference material StHs6/80-G with high Rb (30.07 ppm), Sr (482 ppm), Yb (1.13 ppm) and Er (1.18 ppm). Then, these βRb from Rb-std were applied by linear interpolation to the unknown samples for correction of 87Rb on 87Sr. The analytical results of serial international reference materials (BIR-1G, BCR-2G, BHVO-2G, T1-G and ATHO-G) demonstrate that our improved method can raise the upper limit of Rb/Sr for in-situ Sr isotope determination and reduce the relative standard deviation of results. This improvement of the upper limit of Rb/Sr (<0.33) will expand not only range of microanalysis for silicate minerals, but also bulk Sr isotope determination of volcanic rock combining with rapid fusion technique.