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

¹¹C]carbon dioxide was prepared from ¹¹C]cyanide. First, ¹¹C]CH₄ was produced by the (p, α) 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/μmol at end of bombardment (EOB) were obtained in a 15 μA irradiation for 10 min.