Determination of beta emitting impurities 89,90 Sr and 90 Y in sodium molybdate and 99 Mo/ 99 ᵐTc generators by sequential chromatography and three-window liquid scintillation counting

Abstract Radiostrontium isotopes (89,90Sr) are important fission products that may occur as radionuclidic impurities in fission-produced sodium molybdate and 99Mo/99ᵐTc generators used for nuclear medicine. Due to their pure β-emission and radiotoxicity, reliable and rapid analytical methods are required to ensure compliance with pharmacopeial limits. In this study, a rapid analytical procedure was developed for the determination of 89Sr, 90Sr, and its daughter 90Y in sodium molybdate and sodium pertechnetate matrices. The method combines sequential chromatographic separation using an anion-exchange Dowex column followed by Sr-spec extraction chromatography with triple-window liquid scintillation counting (LSC). Quantification was performed using both an analytical solution of simultaneous equations and a non-negative least squares (NNLS) algorithm to resolve spectral overlap among the β-emitters. The procedure provides efficient matrix removal and radiostrontium isolation with average chemical recoveries of 80–82 % for strontium and 83–86 % for yttrium. The minimum detectable activities achieved were 0.998 Bq L −1 for 89Sr, 1.01 Bq L −1 for 90Sr, and 1.004 Bq L −1 for 90Y. Application of the method to five batches of sodium molybdate and 99 mTc generator eluates confirmed radionuclidic impurity levels below the limits specified by the European Pharmacopoeia. The proposed approach enables reliable determination of radiostrontium impurities within approximately 3–4 h, making it suitable for routine quality control of fission-produced radiopharmaceuticals.