IMPROVED PREPARATION OF L-[METHYL-C-11]METHIONINE BY ONLINE [C-11] METHYLATION

On-line [C-11]methylation using [C-11]methyl iodide has been successfully applied to the preparation Of L-[Methyl-C-11]-methionine (C-11-Met). [C-11]Methyl iodide is first trapped in a short column that contains Porapak Q and L-homocysteine thiolactone coated on inert support. The column is then charged with NaOH dissolved in a mixture of ethanol and water to cause the [C-11]methylation. The present method can provide practically pure C-11-Met in radiochemical yield of over 98%. The whole procedure including the sterilization of final product has been completely automated for routine PET use.