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Fluoroform is an interesting motif for the isotopologue labelling of biologically active compounds with fluorine‐18 for PET imaging. However, so far the building block [18F]fluoroform and consequently the [18F]trifluoromethylated products suffered from low molar activities ranging from 0.1 to 30 GBq/µmol due to isotopic dilution under the strongly basic standard radiofluorination conditions. In this article the synthesis of high molar activity [18F]fluoroform is described. By implementing a recently reported novel radiofluorination reagent, [18F]triflyl fluoride, the concentration of base‐cryptand complex in the reaction could be reduced 100‐fold compared to standard radiofluorination conditions and molar activities close to 100 GBq/µmol (at end of [18F]fluoroform synthesis) could be obtained, enabling the imaging of low density receptors. Furthermore, an automated procedure was developed on the commercially available NEPTIS® perform synthesizer to provide access of high molar activity [18F]fluoroform to other PET centres.

A novel strategy for the production of reactive [18F]fluoride has been developed, omitting time consuming azeotropic drying procedures. Gaseous [18F]triflyl fluoride is formed instantaneously at room temperature from hydrated [18F]fluoride, followed by distillation in less than 5 minutes into a dry aprotic solvent, in which dry [18F]fluoride is released in presence of base with >90% radiochemical yield. The reactivity of the [18F]fluoride has been confirmed by reaction with several model compounds and by the synthesis of the PET tracers [18F]fluoroestradiol ([18F]FES) and O-2-[18F]fluoroethyl-l-tyrosine ([18F]FET), providing good isolated radiochemical yields and molar activities of up to 123 GBq μmol-1.

The rapid synthesis and the automatic auto-cleaning procedure allow convenient and reproducible [11C]PIB synthesis to be performed during the same day for preclinical or clinical PET scans.

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