Rapid Aqueous Late-Stage Radiolabelling of [GaF3 (BnMe2 -tacn)] by 18 F/19 F Isotopic Exchange: Towards New PET Imaging Probes.

A simple and rapid method for 18 F radiolabelling of [GaF3 (BnMe2 -tacn)] by 18 F/19 F isotopic exchange is described. The use of MeCN/H2 O or EtOH/H2 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 nm, and 37±5 % 18 F incorporation at even lower concentration (27 nm), without the need for a Lewis acid promoter. A solid-phase extraction method was established to give [Ga18 F19 F2 (BnMe2 -tacn)] in 99 % radiochemical purity in an EtOH/H2 O mixture.