Rapid analysis of ²³⁷Np and Pu isotopes in unseparated sample matrices using ICP-MS/MS

Inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) is an emerging technique for measuring actinide isotopes when assessing pre- and post-detonation nuclear material. In this study, ICP-MS/MS was investigated for direct Np and Pu quantitation in unseparated, dissolved bulk soil matrices. To achieve this, purified nitric oxide (NO) was investigated for the reactivity of Th, Np, U, Pu, Am, and Cm. Purifying NO prior to the collision reaction cell (CRC) results in increased sensitivity and allows for higher gas flows to be utilized for the removal of interferences. The interference from uranium hydrides was mitigated to less than 3.85 x 10^-11. This method was demonstrated on standard reference materials which were measured for ²³⁷Np and ^238,239,240Pu in dilute sample digestions. The ²³⁸Pu measurement was validated by spiking into a standard reference material and was accurately measured with an excess of 85000 of ²³⁸U.