Introduction: This study presents the development of an automated radiosynthesis system integrating a microwave reactor and its subsequent application in the synthesis of [(18)F]flumazenil, a potentially useful compound in the evaluation of central benzodiazepine receptor density.
Methods: Preparation of dry [K/K(222)](+18)F(-) complex and radiofluorination of the nitro-flumazenil precursor were achieved using the developed microwave-based radiosynthesis system. The crude product was prepurified in a C18 cartridge followed by reversed-phase preparative high-performance liquid chromatography. The isolated [(18)F]flumazenil was evaporated in vacuo and reconstituted in an ethanol-free solution.
Results: Optimum incorporation of (18)F(-) in the nitro-precursor was achieved in 5 min time utilizing 2 mg of precursor in N,N-dimethylformamide reacted at 160 degrees C which gave an incorporation yield of 40+/-5%. The radiochemical yield obtained at the end of synthesis was 26+/-4% (EOB) with a radiochemical purity of >99% and a total synthesis time of about 55-60 min. The produced [(18)F]flumazenil was observed to be stable for at least 8 h.
Conclusion: The developed [(18)F]flumazenil radiosynthesis system offers shorter reaction time, simplicity in operation and applicability for use in routine clinical practice.