State Key Laboratory of Loess and Quaternary Geology, Shaanxi Key Laboratory of Accelerator Mass Spectrometry Technology and Application, Xi'an AMS Center , Institute of Earth Environment, Chinese Academy of Sciences , Xi'an 710061 , China.
Center for Nuclear Technologies , Technical University of Denmark, DTU Nutech , Roskilde DK-4000 , Denmark.
Anal Chem. 2019 Sep 17;91(18):11553-11561. doi: 10.1021/acs.analchem.9b01347. Epub 2019 Aug 23.
ICP-MS is becoming a competitive technique for measurement of plutonium isotopes. Besides the abundance sensitivity (tailing of U to / = 239 and 240), isobaric and polyatomic ions interferences (e.g., UH) are the most critical challenges for determination of low-level plutonium in high uranium samples. This work presents a new method to solve this problem using ICP-MS with two tandem quadrupole separators and a dynamic collision/reaction cell combined with chemical separation. The interference of uranium hydrides (UH and UH) was effectively eliminated using CO as reaction gas by converting hydrides to oxides of uranium ions (UO/UO) but still keeping the intensity of the Pu signal. The tailing interference of U (abundance sensitivity) was intensively eliminated by significantly suppressing the U signal using CO as reaction gas and using two tandem quadrupole mass separators in the ICP-MS/MS. With these approaches the overall interference of uranium was reduced to <1 × 10, which is 3 orders of magnitude better than the conventional ICP-MS. Combined with chemical separation with a decontamination factor of 10 for uranium, an overall factor of 10 for elimination of uranium interference was achieved. The developed method was demonstrated to enable accurate determination of <10 g/g level plutonium isotopes in environmental samples even in a uranium debris sample with a U/Pu atomic ratio of up to 10. The developed method was validated by analysis of a spiked solution and certified reference materials of soil.
电感耦合等离子体质谱（ICP-MS）正成为测量钚同位素的一种有竞争力的技术。除了丰度灵敏度（U 对 239 和 240 的尾随）之外，同量异位素和多原子离子干扰（例如，UH）是在高铀样品中测定低水平钚的最关键挑战。本工作提出了一种新的方法，使用带有两个串联四极杆分离器和动态碰撞/反应池的 ICP-MS 结合化学分离来解决这个问题。通过将氢化物转化为铀离子的氧化物（UO/UO），同时保持 Pu 信号的强度，使用 CO 作为反应气体有效地消除了铀氢化物（UH 和 UH）的干扰。通过使用 CO 作为反应气体并在 ICP-MS/MS 中使用两个串联四极杆质量分离器显著抑制 U 信号，强烈消除了 U 的尾随干扰（丰度灵敏度）。通过这些方法，总的铀干扰降低到 <1×10，比传统的 ICP-MS 好 3 个数量级。结合铀的去污因子为 10 的化学分离，实现了铀干扰消除的总因子为 10。即使在 U/Pu 原子比高达 10 的铀碎片样品中，该方法也被证明可以准确测定 <10 g/g 级别的环境样品中的钚同位素。通过对加标溶液和土壤标准物质的分析验证了该方法的有效性。
