A rapid method suitable for the routine preparation of [11C]acetic and [11C]palmitic acids is described. The reaction of [11C]carbon dioxide with a Grignard reagent and purification by liquid-liquid extraction were carried out in a liquid layer supported by a commercially available kieselguhr, ExtrelutR (Merck). [11C]Carbon dioxide was efficiently trapped into a reagent solution kept by an Extrelut column and the free [11C]fatty acid formed by quenching with diluted HCl was sequentially extracted by flowing an appropriate organic solvent from the reaction column into the solvent and then from the solvent into a short column of Extrelut for [11C]acetic acid or silica gel for [11C]palmitic acid. Thus, using this on-line method based on column extraction, [11C]acetic acid was prepared in over 90% radiochemical yield and [11C]palmitic acid in approx. 50% radiochemical yield, within 15 min, with the same system and procedure.
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