Evaluation of a chloride-based ⁸⁹Zr isolation strategy using a tributyl phosphate (TBP)-functionalized extraction...

The remarkable stability of the ⁸⁹Zr-DOTA complex has been shown in recent literature. The formation of this complex appears to require ⁸⁹Zr-chloride as the complexation precursor rather than the more conventional ⁸⁹Zr-oxalate. In this work we present a method for the direct isolation of ⁸⁹Zr-chloride from irradiated ^natY foils.

⁸⁹Zr, ⁸⁸Zr, and ⁸⁸Y were prepared by 16 MeV proton irradiation of ^natY foils and used for batch-extraction based equilibrium coefficient measurements for TBP and UTEVA resin. Radionuclidically pure ⁸⁹Zr was prepared by 14 MeV proton-irradiation of ^natY foils. These foils were dissolved in concentrated HCl, trapped on columns of TBP or UTEVA resin, and ⁸⁹Zr-chloride was eluted in <1 mL of 0.1 M HCl. For purposes of comparison, conventionally-isolated ⁸⁹Zr-oxalate was converted to ⁸⁹Zr-chloride by trapping, rinsing, and elution from a QMA cartridge into 1 M HCl. Trace metal analysis was performed on the resulting ⁸⁹Zr products.

Equilibrium coefficients for Y and Zr were similar between UTEVA and TBP resins across all HCl concentrations. K_d values of <10^-1 mL/g were observed for Y across all HCl concentrations. K_d values of >10³ mL/g were observed at HCl concentrations >9 M for Zr, falling to K_d values of <10⁰ mL/g at low HCl concentrations. ⁸⁹Zr-chloride was recovered from small columns of TBP in <1 mL of 0.1 M HCl with an overall recovery efficiency of 89 ± 3% (n = 3). An average Y/Zr separation factor of 1.5 × 10⁵ (n = 3) was obtained. Trace metal impurities, notably Fe, were higher in TBP-isolated ⁸⁹Zr-chloride compared with ⁸⁹Zr-chloride prepared using the conventional two-step procedure.

TBP-functionalized resin appears promising for the direct isolation of ⁸⁹Zr-chloride from irradiated ^natY targets. Excellent ⁸⁹Zr recovery efficiencies were obtained, and chemical purity was sufficient for proof-of-concept chelation studies.