Exploitation of nano alumina for the chromatographic separation of clinical grade 188Re from ¹⁸⁸W: a renaissance of the ¹⁸⁸W/¹⁸⁸Re generator technology

Abstract

The ¹⁸⁸W/¹⁸⁸Re generator using an acidic alumina column for chromatographic separation of ¹⁸⁸Re has remained the most popular procedure world over. The capacity of bulk alumina for taking up tungstate ions is limited (∼50 mg W/g) necessitating the use of very high specific activity ¹⁸⁸W (185–370 GBq/g), which can be produced only in very few high flux reactors available in the world. In this context, the use of high-capacity sorbents would not only mitigate the requirement of high specific activity ¹⁸⁸W but also facilitate easy access to ¹⁸⁸Re. A solid state mechanochemical approach to synthesize nanocrystalline γ-Al₂O₃ possessing very high W-sorption capacity (500 mg W/g) was developed. The structural and other investigations of the material were carried out using X-ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer Emmett Teller (BET) surface area analysis, thermogravimetric-differential thermal analysis (TG-DTA), and dynamic light scattering (DLS) techniques. The synthesized material had an average crystallite size of ∼5 nm and surface area of 252 ± 10 m²/g. Sorption characteristics such as distribution ratios (K_d), capacity, breakthrough profile, and elution behavior were investigated to ensure quantitative uptake of ¹⁸⁸W and selective elution of ¹⁸⁸Re. A 11.1 GBq (300 mCi) ¹⁸⁸W/¹⁸⁸Re generator was developed using nanocrystalline γ-Al₂O₃, and its performance was evaluated for a period of 6 months. The overall yield of ¹⁸⁸Re was >80%, with >99.999% radionuclidic purity and >99% radiochemical purity. The eluted ¹⁸⁸Re possessed appreciably high radioactive concentration and was compatible for the preparation of ¹⁸⁸Re labeled radiopharmaceuticals.