An assessment of radionuclidic impurities of 210Po produced via neutron irradiation of 209Bi for use in targeted alpha-particle radiotherapy

Radionuclidic impurities of 210Po prepared by neutron irradiation of 209Bi via the 209Bi(n,γ)210Bi reaction were investigated. Following irradiation and ingrowth, a pure 210Po solution was obtained by sublimation and dissolution. Results were obtained by liquid scintillation (LS) counting, isotope dilution alpha (α)-spectrometry, and high-purity germanium gamma-ray spectrometry. No alpha-emitting (3–10 MeV) or gamma-emitting (30–3600 keV) impurities were detected, with calculated lower limits of detection for impurities of approximately 0.01% 210Po activity. LS spectra revealed no identifiable beta-emitting impurity. LS sources prepared using Opti-Phase ‘Hi Safe’ III and Opti-Fluor LS cocktails were stable over a 4-day multi-cycle counting period for 210Po dissolved in 0.1% trifluoracetic acid (pH ∼2, water fraction ∼2%). The radioactivity concentration determined by LS counting was verified by isotope dilution alpha spectrometry. These results suggest that neutron irradiation of 209Bi (followed by sublimation) can produce 210Po in a highly pure form that is suitable for radiopharmaceutical preparations.