水样中237Np、239~241Pu和241Am快速同时分析

Rapid Simultaneous Determination of 237Np, 239-241Pu and 241Am in Water Samples

  • 摘要: 核应急状况下需要对放射性污染的水平和程度进行快速评估,其中高毒性超铀核素(237Np、239~241Pu和241Am)的快速同时分析尤为重要。然而针对同一样品中多种难分析放射性核素的测定,目前报道的方法需要使用多种色谱分离树脂对其分别进行分离,操作流程繁琐耗时,难以满足快速响应的需求。本工作将基于DGA树脂的核素色谱分离与三重四极杆电感耦合等离子体质谱(ICP-MS/MS)测量技术相结合,建立了一种能够同时测定水样中多种超铀核素的快速分析方法。该方法分别使用242Pu和243Am作为Np/Pu和Am的示踪剂,化学产率均大于80%。使用ICP-MS/MS的He-O2模式,基于237Np、239~241Pu和241Am与O2的反应速率不同,实现了同一待测液中所有目标核素浓度的直接同时测量。实验表明,在8.0 mL/min He-0.37 mL/min O2条件下,241Pu和241Am的交叉污染小于1%。方法对这些超铀核素的检测限达到fg量级,每批样品的分析时间小于2.5 h,满足核应急分析需求。使用标准加入法对建立的分析方法进行了验证,结果表明其准确可靠。

     

    Abstract: In nuclear emergency, it is crucial to quick assess the level and extent of radioactive contamination. Highly toxic transuranic nuclides (237Np, 239-241Pu and 241Am) are the most important radionuclides in radioactive contamination. In the case for analysis of multiple radionuclides in the same sample, the reported analytical methods are often time-consuming/tedious by using multiple chromatographic separation resins for the separation of every single radionuclide. In this work, a rapid analytical method for simultaneously determining transuranium nuclides in water samples was developed by coupling triple quadrupole inductively coupled plasma mass spectrometry (ICP-MS/MS) with a single DGA resin column, Np, Pu, and Am were simultaneously enriched and purified. For monitoring chemical yields of Np/Pu and Am, the chemical recoveries are greater than 80% which is monitored using 242Pu and 243Am as tracers. O2 was used as reaction gas in the collision reaction cell (CRC) of ICP-MS/MS, the chemical reaction behavior of Np and Pu with O2 is similar, and Np/Pu reacts with O2 and converts to \mathrmNpO_2^+ /\mathrmPuO_2^+ , and Am reacts with O2 and concerts to AmO+. 237Np, 239-241Pu and 241Am in the same solution were simultaneously measured by the He-O2 mode of ICP-MS/MS in the same run, and the cross contamination of 241Pu and 241Am (<1%) was achieved using 8.0 mL/min He-0.37 mL/min O2 as reaction gas. A sensitivity of 814×106 s−1/(mg/L) for Np, 799×106 s−1/(mg/L) for Pu, and 1 027×106 s−1/(mg/L) for Am is achieved, and the sensitivity ratio of \mathrmNpO_2^+ and \mathrmPuO_2^+ is close to 1, indicating that 242Pu is feasible as a non-isotope tracer of Np under this condition. The abundance sensitivity of U and the interference of polyatomic ions (1H238U+, 1H2238U+, 206Pb35Cl+, 204Pb37Cl+, 204Hg37Cl+, 205Tl36Ar+ and ^209\mathrmBi^16\mathrmO_2^+) formed by U and matrix elements (Pb, Hg, Tl and Bi) are effectively inhibited. The detection limit (DL) of 1.84 fg/L for 237Np, 2.08 fg/L for 239Pu, 0.70 fg/L for 240Pu, 0.66 fg/L for 241Pu and 1.27 fg/L for 241Am are approached, this is three orders of magnitude lower than the DL required in nuclear emergency situations (1 Bq/L). The developed method is validated by analyzing the spiked samples, and allows for the rapid, simultaneous detection of ultra-trace amounts of Np, Pu and Am in environmental water samples within 2.5 h. This significantly reduces analysis time and meets the requirement for emergency preparedness.

     

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