A comprehensive survey of reference materials for their use in quality assurance for the determination of Np-237 in environmental samples.

Neptunium-237 ( ²³⁷ Np) is one of the most hazardous radionuclides of public concern due to its radiological toxicity, long half-life and high environmental mobility. Standard reference materials (SRMs) with well characterized ²³⁷ Np activity concentrations are valuable for method development and validation of ²³⁷ Np determination in environmental samples. In this study, a comprehensive literature survey of ²³⁷ Np activity concentrations in 25 SRMs was carried out covering the various matrices of sediment, soil, seawater, atmospheric particles, and biota. After data screening, arithmetic mean of the activity concentrations of ²³⁷ Np in literatures were calculated as statistical values (SVs). Then, accuracies of different instrument analyses and acid digestion methods were evaluated based on the SVs. Finally, by optimizing the sector field ICP-MS analytical method, ²³⁷ Np activity concentration in JSAC-0471 soil SRM was measured. The application of SVs provides ²³⁷ Np activity concentration information in more SRMs. Besides SRMs certified by technically validated procedures, SRMs with SVs and the measurement of JASC-0471 provide more options for suitable selection of SRMs for ²³⁷ Np determination.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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