Column extraction method for rapid preparation of [¹¹C]acetic and [¹¹C]palmitic acids

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, Extrelut^R (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.