Precise Determination of Cd Isotope Ratios at 3–10 ng Level by Thermal Ionization Mass Spectrometry Using a Molybdenum Silicide Emitter,Analytical Chemistry

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Precise Determination of Cd Isotope Ratios at 3–10 ng Level by Thermal Ionization Mass Spectrometry Using a Molybdenum Silicide Emitter
Analytical Chemistry ( IF 6.7 ) Pub Date : 2024-09-10 , DOI: 10.1021/acs.analchem.4c03362
Chao-Feng Li _{1,

2} , Zhu-Yin Chu _{1,

2} , Peng Peng _{1,

2}

Affiliation

Thermal ionization mass spectrometry (TIMS) combined with the double spike technique has excellent analytical precision for Cd isotopic ratio analysis. However, because of the low ionization efficiency of Cd by TIMS, it is still not possible to obtain high precision Cd isotope ratios for small sample size (<100 ng) due to the lack of a highly sensitive emitter for Cd. A new loading method using molybdenum silicide (MoSi₂) emitter has been developed for Cd isotope ratio measurements. This emitter produces a significant enhancement in the ionization efficiency of Cd and thus significantly reduces the required sample size to the 3–10 ng level. Analyses of δ^114/110Cd for the NIST SRM 3108 using ¹⁰⁸Cd–¹¹⁶Cd double spike method show excellent reproducibility (2 SD) that reaches ±0.032‰, ±0.042‰, and ±0.051‰ for 10, 5, and 3 ng of Cd, respectively. This method was further verified with a suite of geological reference materials. Replicate digestions and analyses (n = 8, 2 SD) of δ^114/110Cd for NIST SRM 2711a, NOD A-1, and GBW08401 demonstrated good external reproducibility with results of 0.596 ± 0.024‰ for NIST SRM 2711a, 0.150 ± 0.036‰ for NOD A-1, and −0.665 ± 0.084‰ for GBW08401. These data clearly indicate that MoSi₂ is an excellent alternative for traditional silica gel to Cd isotopic measurements, especially for samples with a low content of Cd.

中文翻译：

使用硅化钼发射器通过热电离质谱法精确测定 3–10 ng 水平的 Cd 同位素比

热电离质谱 (TIMS) 与双尖峰技术相结合，对于 Cd 同位素比分析具有出色的分析精度。然而，由于TIMS对Cd的电离效率较低，由于缺乏高灵敏度的Cd发射器，仍然无法在小样品量（<100 ng）下获得高精度的Cd同位素比。已经开发出一种使用硅化钼 (MoSi ₂ ) 发射器的新加载方法，用于 Cd 同位素比测量。该发射器显着提高了 Cd 的电离效率，从而将所需的样品量显着减少到 3-10 ng 水平。使用¹⁰⁸ Cd– ¹¹⁶ Cd 双尖峰方法对 NIST SRM 3108 的 δ ^114/110 Cd 进行分析，显示出出色的重现性 (2 SD)，对于 10、5 和 3 ng 达到 ±0.032 ‰、±0.042 ‰ 和 ±0.051 ‰分别为 Cd。该方法通过一套地质参考资料得到进一步验证。 NIST SRM 2711a、NODA-1 和 GBW08401 的 δ ^114/110 Cd 重复消解和分析 ( n = 8, 2 SD) 表现出良好的外部重现性，NIST SRM 2711a 的结果为 0.596 ± 0.024 ‰，NIST SRM 2711a 为 0.150 ± 0.036 ‰对于 NOD A-1，对于 GBW08401 为 −0.665 ± 0.084‰。这些数据清楚地表明，MoSi ₂是传统硅胶 Cd 同位素测量的绝佳替代品，特别是对于 Cd 含量较低的样品。

更新日期：2024-09-10

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