Preparation of 11C-labelled methanol on

E. Sarkadi, Z. Kovacs, P. Lehikoinen and G. Horvath
 Abo Academy, Turku, Finland
 PET Center, University School of Medicine, Debrecen
The [11C]methyl iodide is an important intermedier to synthesize 11C-labelled
radiopharmaceuticals for medical diagnostics in positron emission tomography.
As a rst step of the [11C]methyl iodide preparation [1, 2] the classical ra-
diomethanol production has been applied in our laboratory earlier [3]. Recently
we have developed a new method to produce [11C]methanol intermedier.
[11C]carbon dioxide was produced by the 14N(p,)11C nuclear reaction, irradi-
ating nitrogen gas (containing oxigen in ppm level) with 15 MeV protons at the
Debrecen and Turku compact MGC-20 cyclotrons. Trapping of the [11C]carbon
dioxide, produced and previously concentrated in a freezing unit, was carried out at
room temperature on an alumina column properly impregnated with lithium alu-
minum hydride dissolved in tetrahydofuran. The whole alumina column had to be
impregnated, otherwise the dry part of the alumina would adsorb the [11C]carbon
dioxide without complex formation (lithium aluminum [11C]methylate) and, after
heating the column up to 180 C in order to eliminate the solvent, the unreacted
[11C]carbon dioxide would leave with the helium carrier gas.
After the elimination of tetrahydrofuran the [11C]methanol was produced by
hydrolyzing of the complex (with introduction of water) at 180 C. Conversion of
the released [11C]methanol into [11C]methyl iodide was carried out by the hydrogen
iodide { alumina method described in [4].
The advantage of this method of radiomethanol preparation is the application of
an alumina column at room temperature instead of a complicated cooling unit used
with the conventional reaction vessel. The big surface of the alumina wetted with
lithium aluminum hydride assures the shorter reaction time. The construction of this
synthesis system is simple and more reliable. The yield and purity of radiomethanol
was the same as in the previous methods.
[1] D. Comar, M. Maziere, Radiopharm. Lab. Comp. Vol. 1, IAEA, Vienna (1974)
461
[2] G. Berger, M. Maziere, Appl. Radiat. Isot. 30 (1979) 393
[3]  E. Sarkadi, Z. Kovacs, ATOMKI Annual Report (1994) 78
[4]  E. Sarkadi, Z. Kovacs, Radiochimica Acta 76 (1997)