Production and Transport of Gaseous (18)F-Synthons: (18)F-Acyl Fluorides.

Fluorine-18 ((18)F, T 1/2=109.7 min) is a positron-emitting isotope that has found extensive application as a radiolabel for positron emission tomography (PET). Although gaseous (11)C-CO2 and (11)C-CH4 are practically transported from cyclotron to radiochemistry processes, (18)F-fluoride is routinely transported in aqueous solution because it is commonly produced by proton irradiation of (18)O-enriched water. In most cases, subsequent dry-down steps are necessary to prepare reactive (18)F-fluoride for radiofluorination. In this work, a simple module was designed to generate gaseous (18)F-acyl fluorides from aqueous (18)F-fluoride solution by solid phase (18)F-radiofluorination of acyl anhydride. The gaseous (18)F-acyl fluorides were purified through a column containing Porapak Q/Na2SO4, resulting in high yields (>86%), purities (>99%) and specific activities (>1200 GBq/μmol). Prototypic (18)F-acetyl fluoride ((18)F-AcF) was readily transported through 15 m of 0.8 mm ID polypropylene tubing with low (0.64 ± 0.12 %) adsorption to the tubing. Following dissolution of (18)F-AcF in solvent containing base, highly reactive (18)F-flouride was generated immediately and used directly for (18)F-labeling reactions. These data indicate that (18)F-acyl fluorides represent a new paradigm for preparation and transport of anhydrous, reactive (18)F-fluoride for radiofluorinations.