Purification of a Au tracer from a Pt target using UTEVA resin column chromatography.

Radioactive 195Au is useful for the long-term biodistribution tracking of gold nanoparticles in cancer diagnostics and therapeutics. This study develops a highly selective separation method for 195Au produced via the charged particle irradiation of a Pt target using UTEVA resin column chromatography and elucidates the underlying separation mechanism. To optimize the chromatographic conditions, batch experiments were performed with the UTEVA resin in HCl and HNO3 media using tracer amounts of 195Au and macro amounts of Pt. 195Au exhibited high distribution coefficients in HCl, whereas Pt showed negligible adsorption. In HNO3 media, the distribution coefficients of 195Au decreased with increasing acid concentration. Subsequent two-step column chromatography using the UTEVA resin achieved a chemical yield of 91.6% and a decontamination factor of 4.6 × 103 for Pt. To understand this selectivity, density functional theory (DFT) calculations were performed on the interactions between the anionic chloride complexes of Au, Pt, and Ir (a by-product of the nuclear reaction) and the protonated phosphonate cation. The calculations revealed that the Gibbs free energy change for ion-pair formation follows the order of Au < Ir < Pt, suggesting that anionic chloride complexes of Au readily form ion-pair complexes and are extracted. This extraction of Au is driven by a lower dehydration energy and reduced steric hindrance of [AuCl4]- compared to the highly charged and octahedral [PtCl6]2- and [IrCl6]2- ions. This study demonstrates that the UTEVA resin is highly effective for the separation and purification of 195Au from irradiated Pt targets. The purified 195Au obtained by this method can be utilized in future research on Au nanoparticles.