[11C]Methyl iodide is the principle reagent for introduction of C-11 into radio-pharmaceuticals. Although there have been many variations on the method used for its production, all methods involve the reduction of [11C]C02 with LiAIH4 to provide the [11C]methyl alkoxy aluminate followed by conversion in HI to [11C]CH3I. There are two problems with the existing methodology. First, even under the most carefully controlled conditions, the specific activity of [11C]CH3I can be significantly lowered by absorption of atmospheric C02 and carbonaceous material in the LiAIH4 reagent solvent. Second, the methyl alkoxy aluminate and excess LiAIH4 must be decomposed to liberate [11C]methanol prior to solvolysis to [11C]CH3I. This requires that any residual activity must be allowed to decay and the apparatus thoroughly cleaned, dried and set-up before additional preparations. This research will examine the feasibility of selective on-line functionalization of [11C]methane over various supported Lewis acid and platinum catalyst1. [11C]C02 is quantitatively converted to [11C]CH4 by passage over Ni catalyst at 400degreesC. Methane has been reported to be converted to methyl trifluoromethanesulfonate (methyl triflate) by reaction with stoichiometric amounts of mercury(II) triflate in trifflic acid at 180degreesC2. [11C]Methyl triflate is highly reactive alkylating agent with physical and chemical properties particularly suited to the microscale of radio-labeling chemistry3. A new C-11 target manifold has been designed and fabricated which allows for the on-line analysis of target gases and products obtained from subsequent chemistry. The GC utilizes a state of the art helium discharge ionization detector (DID) capable of detecting products in the 50 ppb range, slightly below that necessary for high specific determinations.
