Radio high pressure liquid chromatography (radio-HPLC) is the method of choice for quality control of radiopharmaceuticals
labelled with short lived isotopes. Our preparations of “no carrier added”11C-labelled palmitic acid and L-methionine are both designed to end with a HPLC separation on either silica gel or C-18 reversed
phase material. Since the crude reaction mixtures contain milligram amounts of inactive substrate materials, both separations
must be carried out at preparative scale. Nevertheless they are performed in less than 10 min. The most critical factor for
the separation of11C-palmitic acid from the main by-product pentadecane is the solvent composition: while the11C-L-methionine separation is especially sensitive to pH variations.