Directly determining 143Nd/144Nd isotope ratios using thermal ionization mass spectrometry for geological samples without separation of Sm–Nd
Directly determining 143Nd/144Nd isotope ratios using thermal ionization mass spectrometry for geological samples without separation of Sm–Nd
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DOI：
10.1039/c0ja00081g
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发表时间：
2011-10
影响因子：
3.4
通讯作者：
Chaofeng Li;Xian‐Hua Li;Qiulong Li;Jing-hui Guo;Xianghui Li
中科院分区：
文献类型：
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作者：
Chaofeng Li;Xian‐Hua Li;Qiulong Li;Jing-hui Guo;Xianghui Li
Sm-Nd同位素体系是地球化学和宇宙化学中一种强有力的示踪和定年工具。热电离质谱（TIMS）是获得高精度Nd同位素比值的基准方法。传统上，为了获得高纯度的Nd组分，采用两步分离，这使得样品制备耗时。本文提出了一种不经Sm-Nd分离直接获得地质样品Nd同位素比值的新方法。该方法的关键是要很好地校正144 Sm对144 Nd的同量异位素干扰。利用147 Sm/144 Sm比值为4.87090和147 Sm/149 Sm比值为1.08583，利用Russell公式计算出Sm的质量分辨因子βSm，可以得到144 Sm的准确强度。因此，获得了144 Nd的真实的强度，然后还获得了原始的146 Nd/144 Nd、143 Nd/144 Nd比率。最后，143 Nd/144 Nd比使用遵循指数规律的0.7219的146 Nd/144 Nd比进行归一化。该方法的准确性进行了验证，通过复制TIMS测量的13个国际标准物质的硅酸盐岩石，跨越范围广泛的Sm/Nd从0.13到0.46和散装组合物。岩石标准样品的143 Nd/144 Nd比值的测量值与文献报道值符合良好，误差在± 0.004%以内。我们的新方法缩短了分析过程，显著提高了样品通量，这大大有助于那些需要大数据集和快速分析的研究。
Sm–Nd isotopic system is a powerful tracer and dating tool in geochemistry and cosmochemistry. Thermal ionization mass spectrometry (TIMS) is the benchmark method for obtaining high precision Nd isotope ratios. Traditionally, a two-step separation was employed in order to obtain high purity Nd fraction, which makes the sample preparation time-consuming. In this study, we present a new method to directly obtain precise and accurate Nd isotope ratios of geological samples without Sm–Nd separation. The key point is to well correct isobaric interferences of 144Sm on 144Nd for this method. The accurate intensity of 144Sm can be obtained using 147Sm/144Sm ratio of 4.87090 and mass discrimination factor of Sm (βSm), which is achieved using 147Sm/149Sm ratio of 1.08583 with Russell equation. Consequently, the real intensity of 144Nd was achieved, then also raw 146Nd/144Nd, 143Nd/144Nd ratios. Finally, 143Nd/144Nd ratio is normalized using 146Nd/144Nd ratio of 0.7219 following exponential law. The accuracy of this method is validated by replicating TIMS measurements for thirteen international reference materials of silicate rock, spanning a wide range of Sm/Nd from 0.13 to 0.46 and bulk compositions. The measured 143Nd/144Nd ratios of the rock standards are in good agreement with the reported values of within error of ±0.004%. Our new method shortens the analytical procedure and significantly improves sample throughput which greatly contributes to those studies requiring a large dataset and quick analysis.