Analytical methods for plutonium speciation using CE-ICP-MS: Migration behavior, method validation, and uranium matrix effects

Accurately identifying plutonium (Pu) valence states is critical to the safety and efficiency of nuclear fuel reprocessing. In this study, an analytical method for Pu valence state speciation was developed based on capillary electrophoresis hyphenated to inductively coupled plasma mass spectrometry (CE-ICP-MS), enabling effective separation and quantification of Pu(III), Pu(IV), and Pu(VI). Optimal separation conditions were established using surrogate elements with stable oxidation states and 2-hydroxyisobutyric acid (α-HIBA) as the background electrolyte (BGE). Under optimized conditions, the migration order of Pu valence states was determined as Pu(III) > Pu(VI) > Pu(IV), with a relative standard deviation (RSD) of migration time < 1.5%, indicating excellent analytical repeatability. The method was successfully applied to monitor the reduction of Pu(VI) by zero-valent iron (Fe 0 ), elucidating the valence state transformation kinetics (Pu(VI) → unstable Pu(IV) intermediate → Pu(III)). Notably, the method exhibited robust anti-interference capability in high uranium (U) matrices, maintaining baseline separation of Pu valence states even at a U/Pu ratio of 100. This study provides a novel, reliable approach for Pu speciation analysis in complex nuclear matrices, with significant implications for process control and Pu recovery in nuclear fuel reprocessing.