Production and transport of gaseous 18F-synthons: 18F-acyl fluorides

Fluorine-18 (F-18, T-1/2 = 109.7 mm) is a positron-emitting isotope that has found extensive application as a radiolabel for positron emission tomography (PET). Although gaseous C-11-CO2 and C-11-CH4 are practically transported from cyclotron to radiochemistry processes, F-18-fluoride is routinely transported in aqueous solution because it is commonly produced by proton irradiation of O-18-enriched water. In most cases, subsequent dry-down steps are necessary to prepare reactive F-18-fluoride for radiofluorination. In this work, a simple module was designed to generate gaseous F-18-acyl fluorides from aqueous F-18-fluoride solution by solid phase F-18-radiofluorination of acyl anhydride. The gaseous F-18-acyl fluorides were purified through a column containing Porapak Q/Na2SO4, resulting in high yields (>86%), purities (>99%) and specific activities (>1200 GBq/mu mol). Prototypic F-18-acetyl fluoride (F-18-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 F-18-AcF in solvent containing base, highly reactive F-18-flouride was generated immediately and used directly for F-18-labeling reactions. These data indicate that F-18-acyl fluorides represent a new paradigm for preparation and transport of anhydrous, reactive F-18-fluoride for radiofluorinations. (C) 2015 Elsevier B.V. All rights reserved.