Automated synthesis of radiochemically pure 11C-labeled ethyl, propyl and butyl iodides

Carbon-11 labeled alkyl iodides such as ethyl, propyl and butyl iodides are useful precursors for labeling various tracers for positron emission tomography. In the standard preparing process, which consists of the reaction of Grignard reagents with 11CO2 followed by reduction with lithium aluminum hydride and reaction with HI, the produced 11C-alkyl iodides were applied onto gas chromatography using chromosorb W-HP with 10% OV101 as the liquid phase, to give radiochemically pure 11C-ethyl, 11C-propyl or 11C-butyl iodide without a concomitant byproduct, i.e. 11C-methyl iodide. The automated production system was described.