Separation of cyclotron-produced ⁴⁴Sc from a natural calcium target using a dipentyl pentylphosphonate functionalized...

Significant interest in ⁴⁴Sc as a radioactive synthon to label small molecules for positron emission tomography (PET) imaging has been recently observed. Despite the efforts of several research groups, the ideal ⁴⁴Sc production and separation method remains elusive. Herein, we propose a novel separation method to obtain ⁴⁴Sc from the proton irradiation of calcium targets based on extraction chromatography, which promises to greatly simplify current production methodologies. Using the commercially available Uranium and Tetravalent Actinides (UTEVA) extraction resin we were able to rapidly (<20min) recover >80% of the activity generated at end of bombardment (EoB) in small ~1M HCl fractions (400μL). The chemical purity of the ⁴⁴Sc eluates was evaluated through chelation with DOTA and DTPA, and by trace metal analysis using microwave induced plasma atomic emission spectrometry. The distribution coefficients (K_d) of Sc(III) and Ca(II) in UTEVA were determined in HCl medium in a range of concentrations from zero to 12.1M. The ⁴⁴Sc obtained with our method proved to be suitable for the direct labeling of small biomolecules for PET imaging, with excellent specific activities and radiochemical purity.