Improved production and processing of 89Zr using a solution target

Abstract

ObjectiveThe objectives of the present work were to improve the cyclotron production yield of 89Zr using a solution target, develop a practical synthesis of the hydroxamate resin used to process the target, and develop a biocompatible medium for 89Zr elution from the hydroxamate resin. MethodsA new solution target (BMLT-2) with enhanced heat dissipation capabilities was designed by using helium-cooled dual foils (0.2mm Al and 25μ Havar) and an enhanced water-cooled, elongated solution cavity in the target insert. Irradiations were performed with 14MeV protons on a 2M solution of yttrium nitrate in 1.25M nitric acid at 40-μA beam current for 2h in a closed system. Zirconium-89 was separated from Y by use of a hydroxamate resin. A one-pot synthesis of hydroxamate resin was accomplished by activating the carboxylate groups on a carboxymethyl cation exchange resin using methyl chloroformate followed by reaction with hydroxylamine hydrochloride. After trapping of 89Zr on hydroxamate resin and rinsing the resin with HCl and water to release Y, 89Zr was eluted with 1.2M K2HPO4/KH2PO4 buffer (pH3.5). ICP-MS was used to measure metal contaminants in the final 89Zr solution. ResultsThe BMLT-2 target produced 349±49MBq (9.4±1.2mCi) of 89Zr at the end of irradiation with a specific activity of 1.18±0.79GBq/μg. The hydroxamate resin prepared using the new synthesis method showed a trapping efficiency of 93% with a 75mg resin bed and 96–97% with a 100–120mg resin bed. The elution efficiency of 89Zr with 1.2M K2HPO4/KH2PO4 solution was found to be 91.7±3.7%, compared to >95% for 1M oxalic acid. Elution with phosphate buffer gave very small levels of metal contaminants: Al=0.40–0.86μg (n=2), Fe=1.22±0.71μg (n=3), Y=0.29μg (n=1). ConclusionsThe BMLT-2 target allowed doubling of the beam current for production of 89Zr, resulting in a greater than 2-fold increase in production yield in comparison with a conventional liquid target. The new one-pot synthesis of hydroxamate resin provides a simpler synthesis method for the 89Zr trapping resin. Finally, phosphate buffer elutes the 89Zrfrom the hydroxamate resin in high efficiency while at the same time providing a more biocompatible medium for subsequent use of 89Zr.