Reactivity of electrochemically concentrated anhydrous [18F]fluoride for microfluidic radiosynthesis of 18F-labeled compounds

In order to demonstrate the usefulness of electrochemically concentrated [F-18]fluoride the reactivity of the [K+/K.222] F-18(-) complex concentrated in an aprotic solvent (ca. 60 mu L) was evaluated via nucleophilic F-18-substitution reactions through radiosynthesis of [F-18]FDG, [F-18]FMISO, [F-18]flumazenil and [F-18]fluoromethyl bromide. The substitutions were carried out in a microfluidic reaction flow cell and the effects of reaction time, temperature, precursor concentration and reaction solvent on the F-18-substitution yields were investigated. The F-18-fluorination yields for the four F-18-labeled compounds under optimized conditions (98% for protected [F-18]FDG, 80% for protected [F-18]FMISO, 20% for [F-18]flumazenil and 60% for [F-18]fluoromethyl bromide) were comparable to or higher than those obtained by conventional means. In this study it is clearly demonstrated that electrochemically concentrated [F-18]fluoride enables microfluidic radiosynthesis by effectively reducing synthesis times and especially by increasing radiochemical yields of products labile at high temperatures. (C) 2011 Elsevier Ltd. All rights reserved.