National Institute of Standards and Technology, Materials Measurement Science Division, Gaithersburg, MD, USA.
Analyst. 2018 Dec 17;144(1):317-323. doi: 10.1039/c8an01716f.
The accurate measurement of uranium isotope ratios from trace samples lies at the foundation of achieving nuclear nonproliferation. These challenging measurements necessitate both the continued characterization and evaluation of evolving mass spectrometric technologies as well as the propagation of sound measurement approaches. For the first time in this work, we present the analysis of uranium isotope ratio measurements from discrete liquid injections with an ultra-high-resolution hybrid quadrupole time-of-flight mass spectrometer. Also presented are important measurement considerations for evaluating the performance of this type and other atmospheric pressure and ambient ionization mass spectrometers for uranium isotope analysis. Specifically, as the goal of achieving isotope ratios from as little as a single picogram of solid material is approached, factors such as mass spectral sampling rate, collision induced dissociation (CID) potentials, and mass resolution can dramatically alter the measured isotope ratio as a function of mass loading. We present the ability to accurately measure 235UO2+/238UO2+ down to 10s of picograms of solubilized uranium oxide through a proper consideration of mass spectral parameters while identifying limitations and opportunities for pushing this limit further.
准确测量痕量样品中的铀同位素比值是实现核不扩散的基础。这些具有挑战性的测量既需要不断表征和评估不断发展的质谱技术，也需要传播合理的测量方法。在这项工作中，我们首次展示了使用超高分辨率混合四极杆飞行时间质谱仪对离散液体进样的铀同位素比值测量进行分析。同时还介绍了评估这种类型和其他大气压和环境电离质谱仪进行铀同位素分析的性能的重要测量注意事项。具体而言，随着从仅几皮克固体材料中获得同位素比值的目标的逼近，诸如质谱采样率、碰撞诱导解离（CID）势和质量分辨率等因素会极大地改变作为质量负载函数的测量同位素比值。我们通过适当考虑质谱参数，展示了在识别进一步推动该限制的局限性和机会的同时，准确测量溶解氧化铀中低至数十皮克 235UO2+/238UO2+ 的能力。
