Hoegg Edward D, Marcus R Kenneth, Koppenaal David W, Irvahn Jan, Hager George J, Hart Garret L
Department of Chemistry, Clemson University, 105 Collins St, Clemson, South Carolina, 29634, USA.
Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, WA, 99354, USA.
Rapid Commun Mass Spectrom. 2017 Sep 30;31(18):1534-1540. doi: 10.1002/rcm.7937.
The field of highly accurate and precise isotope ratio analysis, for use in nonproliferation, has been dominated by thermal ionization and inductively coupled plasma mass spectrometry. While these techniques are considered the gold standard for isotope ratio analysis, a downsized instrument capable of accurately and precisely measuring uranium (U) isotope ratios is desirable for field studies or in laboratories with limited infrastructure.
The developed system interfaces the liquid sampling, an atmospheric pressure glow discharge (LS-APGD) ion source, with a high-resolution Exactive Orbitrap mass spectrometer. With this experimental setup certified U isotope standards and unknown samples were analyzed. The accuracy and precision of the system were then determined.
The LS-APGD/Exactive instrument measured a certified reference material of natural U ( U/ U = 0.007261) with a U/ U ratio of 0.007065 and a % relative standard uncertainty of 0.082, meeting the International Target Values for the destructive analysis of U. In addition, when three unknowns were measured and these measurements were compared with the results from an ICP multi-collector instrument, there were no statistical differences between the two instruments.
The LS-APGD/Orbitrap system, while still in the preliminary stages of development, offers highly accurate and precise isotope ratio results that suggest a potential paradigm shift in the world of isotope ratio analysis. Furthermore, the portability of the LS-APGD as an elemental ion source, combined with the small size and smaller operating demands of the Orbitrap, suggests that the instrumentation is capable of being field-deployable.
在用于防扩散的高精度同位素比值分析领域，热电离质谱法和电感耦合等离子体质谱法一直占据主导地位。虽然这些技术被认为是同位素比值分析的金标准，但对于野外研究或基础设施有限的实验室而言，需要一种能够准确测量铀（U）同位素比值的小型仪器。
所开发的系统将液体采样、大气压辉光放电（LS-APGD）离子源与高分辨率Exactive轨道阱质谱仪连接起来。利用该实验装置对认证的U同位素标准物质和未知样品进行了分析，然后确定了该系统的准确性和精密度。
LS-APGD/Exactive仪器对天然U的认证参考物质（U/U = 0.007261）进行测量，得到的U/U比值为0.007065，相对标准不确定度为0.082%，符合U破坏性分析的国际目标值。此外，在对三个未知样品进行测量并将这些测量结果与电感耦合等离子体质谱多接收仪器的结果进行比较时，两台仪器之间没有统计学差异。
LS-APGD/轨道阱系统虽然仍处于开发的初级阶段，但能提供高精度的同位素比值结果，这表明同位素比值分析领域可能会发生范式转变。此外，LS-APGD作为一种元素离子源的便携性，再加上轨道阱的小尺寸和较低的操作要求，表明该仪器能够在野外部署。
