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

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