Preparation of [11C]carbon dioxide from [11C]cyanide.

[11C]Carbon dioxide was prepared from [11C]cyanide. First, [11C]CH4 was produced by the (p, alpha) reaction on a N2/H2 mixture and was converted to [11C]CN- by reaction with ammonia over platinum at 1273 K. The [11C]CN- was adsorbed on a cobalt(II, III) oxide/ceramic furnace material at room temperature and was subsequently converted to [11C]CO2 by heating the cobalt(II, III) oxide to 948 K over a 10 min period and collecting the [11C]CO2 in a trap at 77 K. Specific activities as high as 600 mCi/mumol at end of bombardment (EOB) were obtained in a 15 microA irradiation for 10 min.