Table 2.

Critical parameters in the radiosynthesis of [¹¹C]UCB‐J as determined through repeated experiments (n = 54)

Entry	Parameter/Step	Improvements in Reproducibility Achieved When
1	Drying activated precursor	Drying performed with vacuum in the stream of He
2	Reaction solvent DMF	Dried over molecular sieves. Bottle replaced every 2 weeks
3	Trapping of [11C]CH3I	Reaction volume in reactor 2 increased to 1.1 mL and reactor 2 pressurised before trapping
4	Semi‐prep HPLC purification	Using 5 mL injection loop and diluting the reaction mixture with eluent and filtering prior to injection
5	Quality of [11C]CH3I	Using [11C]CH3I with high molar activity