An automated SPE-based high-yield synthesis of [11C]acetate and [11C]palmitate: no liquid–liquid extraction, solvent evaporation or distillation required

IntroductionAn automated method is described for the rapid and high-yield synthesis of two of the most commonly used radioactive fatty acids: [11C]acetate and [11C]palmitate.MethodsReaction of [11C]CO2 with the respective Grignard reagents in diethyl ether solution proceeded for 2 min at 40°C. Quenching of the reaction and liberation of nonreacted [11C]CO2 occurred upon addition of a fourfold molar excess of aqueous 0.1 M HCl (acetate) or nonaqueous HCl/Et2O (palmitate). Labeled products were then purified by adsorption to an Alumina-N Sep-Pak Plus cartridge and eluted with either aqueous NaH2PO4 solution (acetate) or 100% ethanol (palmitate).ResultsHigh-performance liquid chromatography analysis confirmed that the radiochemical purity of each product was >98%, and decay-corrected radiochemical yields averaged 33% for [11C]palmitate and 40% for [11C]acetate.ConclusionThe method requires no liquid–liquid extraction, solvent evaporation or distillation capabilities and can be readily adapted to existing radiosynthesis modules.