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Description
Molybdenum-93 is a long-lived (t½= 4839(63) y) activation product of increasing relevance for radioactive waste management, yet its determination in complex matrices remains analytically challenging due to its photon and electron emissions (QEC ≈ 406 keV dominant K‑shell X‑rays around 16.5–16.6 keV with associated Auger/conversion electrons) and interferences from chemically similar radionuclides, notably ⁵⁵Fe (QEC ≈ 231 keV, K‑shell X‑rays at ∼5–6 keV with Auger electrons) and ⁶³Ni (Qβ ≈ 67 keV, pure low‑energy β emitter), which have significant overlaps in liquid scintillation counting (LSC) spectra.
In this work, we present an optimised analytical procedure for Mo‑93 determination based on consecutive anion‑exchange chromatographic separation and LSC measurement. Parameters such as separation time, chemical recovery, removal of interferences, efficiency calibration for LSC were investigated and optimized.
Specifically, a detailed elution profile study was performed, enabling a reduction of the total eluent volume while maintaining high chemical recovery of Mo. An aging test was conducted to evaluate the stability of the separation procedure and to quantify potential Mo losses during sample storage and evaporation. In parallel, high‑resolution LC‑ESI‑Orbitrap‑MS was employed to characterise Mo(VI) speciation after column separation and subsequent evaporation of the purified Mo eluates, and to better understand Mo behaviour and mechanism during the separation.
Application of the final optimised procedure to real radioactive waste samples of different types (filter, resin, and metallic waste) yielded Mo recoveries of approximately 50±16% and decontamination factors for key interferents (notably Co, Ni, and Fe) that are compatible with reliable determination of low Mo‑93 activities.