Multiphase extraction: rapid phase-transfer of [18F]fluoride ion for nucleophilic radiolabeling reactions.

In multiphase extraction [18F]fluoride ion for radiolabeling is recovered from target water by passage through a small column of microporous polymer impregnated with a lipophilic cryptand or quaternary ammonium salt. The 18O enriched water can be recovered for reuse. The [18F]fluoride ion-pair is eluted from the column by a small volume of acetonitrile or other organic solvent. Evaporation of the acetonitrile removes traces of water to yield a reactive ion pair for nucleophilic radiofluorination reactions. A wide range of ion-pairs based on K+ or NH+4 cryptands or quaternary ammonium salts can be employed. The method was applied to the synthesis of [18F]FDG.