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This Article Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Chun, J.-H. Articles by Pike, V. PubMed Articles by Chun, J.-H. Articles by Pike, V.

Efficient [¹⁸F]fluorination of a diaryliodonium salt in a micro-reactor

¹ Molecular Imaging Branch, NIMH/NIH, Bethesda, Maryland

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Objectives: Due to a largely unfulfilled need for simple methods to introduce fluorine-18 into an electron-rich aryl ring present in many radiotracers for PET imaging, diaryliodonium salts are gaining interest as precursors for fluorination with ¹⁸F^-. Also there is growing interest in the potential advantages of miniaturizing ¹⁸F-radiochemistry reactors and apparatus. Here we used the reaction of ¹⁸F^- with diphenyliodonium tosylate as a model to demonstrate the feasibility and efficiency of using a microfluidic device for such reactions.

Methods: Cyclotron-produced ¹⁸F^- in H₂¹⁸O was trapped on a QMA cartridge and then released into a solution of K₂CO₃ (0.8 mg) and K2.2.2 (4.5 mg) in MeCN-H₂O (9: 1 v/v; 150 µL). Water was removed by two azeotropic evaporations with MeCN. The resulting ¹⁸F^--K2.2.2-K⁺ complex (0.1–1 mCi/10 µL) and diphenyliodonium tosylate (40 µg/10 µL), both in MeCN, were delivered from two separate storage loops (each 255 µL) to either a 2 or 4 m coiled tube micro-reactor. The reaction mixture was quenched with MeCN-H₂O (1: 1 v/v, 1 mL). The radical scavenger TEMPO was added to some reactions. Amounts of precursor, temperature and flow rates were varied. Decay-corrected radiochemical yields (RCYs) of [¹⁸F]fluorobenzene were measured with radio-HPLC.

Results: The RCYs of [¹⁸F]fluorobenzene ranged from 7 to 81% with TEMPO and from 2 to 40% without TEMPO. A small amount of precursor (40 or 80 µg) sufficed for each of ten different reactions. Reaction times were between 50 and 190 s. Overall processing times were between 3 and 8 min, depending on reactor length and reagent flow rates.

Conclusions: The micro-fluidic device proved very effective for rapidly optimizing the conditions of the radiofluorination reaction and was efficient in producing high RCYs of [¹⁸F]fluorobenzene from small amounts of precursor in short times.

Research Support: IRP, NIMH, NIH

This Article Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Chun, J.-H. Articles by Pike, V. PubMed Articles by Chun, J.-H. Articles by Pike, V.