Electrochemical cell for separation of [18F]fluoride from irradiated 18O-water and subsequent no carrier added nucleophilic fluorination

An electrochemical cell was designed allowing the anodic deposition of n.c.a. [18F]fluoride solubilized in an 18O-water target and subsequent n.c.a. nucleophilic 18F-fluorination. The recovery of the deposited [18F]fluoride can be achieved in the presence of an aprotic solvent containing a phase-transfer catalyst (PTC). The radioisotope adsorbed electrochemically at the cylindrical surface of a glassy carbon electrode can be dried easily by washing the cell twice with dry aprotic solvents while maintaining a low electric field. This simple washing step makes an azeotropic drying process obsolete. Accordingly, less basic cryptates like [Ksubset of2.2.2.]oxalate or triflate can be used for nucleophilic 18F-fluorination because loss of activity as a consequence of azeotropic drying under conditions of low basicity does not occur. The usefulness of this technique is exemplified for the n.c.a. synthesis of various 18F-labelled compounds. The radiotracers were synthesized with higher radiochemical yields and under much easier conditions than the conventional 18F-fluorination procedure which includes an additional drying step of the PTC.