Rapid Aqueous Late‐Stage Radiolabelling of [GaF 3 (BnMe 2 ‐tacn)] by 18 F/ 19 F Isotopic Exchange: Towards New PET Imaging Probes

A simple and rapid method for 18 F radiolabelling of [GaF 3 (BnMe 2 ‐tacn)] by 18 F/ 19 F isotopic exchange is described. The use of MeCN/H 2 O or EtOH/H 2 O (75:25) and aqueous [ 18 F]F − (up to 200 MBq) with heating (80 °C, 10 min) gave 66±4 % 18 F incorporation at a concentration of 268 n m , and 37±5 % 18 F incorporation at even lower concentration (27 n m ), without the need for a Lewis acid promoter. A solid‐phase extraction method was established to give [Ga 18 F 19 F 2 (BnMe 2 ‐tacn)] in 99 % radiochemical purity in an EtOH/H 2 O mixture.