Influential Factors of Liquid Phase Method to Synthesize ¹¹C-CH₃I

¹¹C-CH₃I is a very important methylated precursor in radiopharmaceuticals methylation, however, its yield is low since the ¹¹C half-decay time is short and its synthesis condition is difficult. Most possible factors effect on ¹¹C-CH₃I synthesis yield were investigated, such as the release rate of ¹¹CO₂ from cyclotron target, the release time of ¹¹CO₂ by capture ring (LOOP ring), the evaporation time of THF, the volum of THF with LiAlH₄, the quantity of 57% HI, and the cooling time of reaction tube. After the 10 th system temperature of the module was optimized, the synthesis yield of ¹¹C-CH₃I was 85%±2.3%, the radiochemical purity was more than 99%. Mean while, the results indicated that the main factors of synthesis yield were the the volum of THF with LiAlH₄ and the quantity of 57% HI.