The use of carbon dioxide as the reaction cell gas for the separation of uranium and plutonium in quadrupole inductively coupled plasma mass spectrometry (ICP-MS) for nuclear forensic samples

The use of carbon dioxide (CO₂) as a reaction cell gas for separation and trace analysis of uranium and plutonium by inductively coupled plasma mass spectrometry was investigated. For the analysis of the resultant UO₂⁺ product ion, it was shown that quantitative determination of uranium concentration was achievable within ± 7% uncertainty for samples containing plutonium. In addition, uranium isotope ratios were measured within ± 12% for standard reference materials of several enrichments. This was achieved in both nitric acid and digested cellulose filter paper solutions - a common nuclear forensic sample substrate. However, non-linearity and long term signal instability was observed for plutonium at the high flow rate of CO₂ and tuning parameters required to minimise uranium interferences. Therefore, plutonium analysis was not achievable. (author)