Dowell Sophia M, Barlow Thomas S, Chenery Simon R, Humphrey Olivier S, Isaboke Job, Blake William H, Osano Odipo, Watts Michael J
Inorganic Geochemistry, Centre for Environmental Geochemistry, British Geological Survey, Nottingham, NG12 5GG, UK.
School of Geography, Earth and Environmental Sciences, University of Plymouth, Plymouth, Devon, PL4 8AA, UK.
Anal Methods. 2023 Aug 31;15(34):4226-4235. doi: 10.1039/d3ay01030a.
The analysis of plutonium (Pu) in soil samples can inform the understanding of soil erosion processes globally. However, there are specific challenges associated for analysis in tropical soils and so an optimal analytical methodology ensuring best sensitivity is critical. This method aimed to demonstrate the feasibility of sample preparation and analysis of Pu isotopes in African soils, considering the environmental and cost implications applicable to low-resource laboratories. The separation procedure builds upon previous work using TEVA columns, further demonstrating their usefulness for the reduction of uranium (U) interference in ICP-MS analysis with enhanced selectivity for Pu. Here several steps were optimised to enhance Pu recovery, reducing method blank concentration, and improving the separation efficiency through the determination of the elution profiles of U and Pu. The elimination of the complexing agent in the eluent, increased the spike recovery by improving matrix tolerance of the plasma, and simplified the separation procedure, improving throughput by 20%. The subsequent method was validated through the analysis of Certified Reference Material IAEA-384, where high accuracy and improved precision of measurement were demonstrated (measured value 114 ± 12 versus certified value 108 ± 13 Bq kg). Optimisation of the column separation, along with the analysis of the samples using O gas in ICP-MS/MS mode to mass shift Pu isotopes away from interfering molecular U ions provided a simple, robust, and cost-effective method with low achievable method detection limits of 0.18 pg kgPu, applicable to the detection of ultra-trace fallout Pu in African soils.
对土壤样品中钚（Pu）的分析有助于全球范围内对土壤侵蚀过程的理解。然而，热带土壤分析存在特定挑战，因此确保最佳灵敏度的最佳分析方法至关重要。该方法旨在证明非洲土壤中钚同位素样品制备和分析的可行性，同时考虑到适用于资源匮乏实验室的环境和成本因素。分离程序基于先前使用TEVA柱的工作，进一步证明了它们在电感耦合等离子体质谱（ICP-MS）分析中减少铀（U）干扰以及对钚具有更高选择性方面的有用性。这里优化了几个步骤以提高钚的回收率、降低方法空白浓度，并通过测定铀和钚的洗脱曲线来提高分离效率。去除洗脱液中的络合剂提高了加标回收率，通过改善等离子体的基质耐受性实现，简化了分离程序，使通量提高了20%。随后通过对国际原子能机构认证参考物质IAEA-384的分析验证了该方法，结果显示出高准确度和改进的测量精密度（测量值114±12与认证值108±13 Bq/kg）。柱分离的优化，以及在ICP-MS/MS模式下使用氧气对样品进行分析以使钚同位素从干扰分子铀离子中质量偏移开来，提供了一种简单、稳健且经济高效的方法，并具有低至0.18 pg/kg钚的可实现方法检测限，适用于检测非洲土壤中的超痕量沉降钚。
