A new strategy for facile and rapid separation of astatine-211 from nitric acid medium

Developing fast and efficient separation avenues can promote either fundamental study or practical application of astatine-211(At-211). This work presents a new solid-phase extraction (SPE) separation strategy based on functional resin for recovering At-211 from the irradiated bismuth (Bi) target mildly and rapidly, without switching HNO3 medium into HCl system. Four functional resins containing acyl-resin, thioether, sulfonate- and sulfonate-groups had been prepared via Friedel-Crafts acylation and alkylation reactions successfully, and subsequently characterized by FTIR, EA, SEM etc. Acyl-resin from these functional materials have shown good retention towards At-211 but low binding affinity to all possible metal impurities (Zn2+, Cu2+, Ga(3+)and Bi3+) in simulated separation experiments. Static batch sorption experiments indicate that the pseudo-second-order kinetic model is more suitable for describing the binding behavior of At-211 on Acyl-resin. This reveals that chemisorption dominates the reaction between the target radionuclide and functional material. During several practical separations in medically-used scale, over 98.5 % of At-211 can be well retained on SPE column with metal impurities removed in the process of loading target solution and removing non-target radionuclides. More importantly, 60.03 %similar to 79.05 % of At-211 on the Acyl-resin SPE column is recoverable by NH2OH-NH3H2O-CH3OH elution process, and over 60 % of the radioactivity distributes in volatile organic solvent (CH3OH). The whole SPE separation process can be completed within 20 min, giving At-211 product with high radionuclidic purity (>= 99 %), low metal impurities (Bi3+<= 17.37 mu g and Cu2+<= 2.91 mu g) and high radiolabeling availability. This work implies that acyl-groups can act as potential binding motifs not only for developing new At-211 separation methods but also designing bifunctional conjugate agents for astatinated compounds based on coordination bonds.

Automated summary

This study presents a new solid-phase extraction (SPE) separation strategy for recovering astatine-211 (At-211) from irradiated bismuth targets. The use of acyl-resin as a functional material showed good retention of At-211 and low binding affinity to metal impurities. The SPE separation process can be completed within 20 minutes, providing At-211 product with high radionuclidic purity and low metal impurities. This method has potential applications in medical-scale separations.