¹¹C.

Any no-carrier-added **1**1C-compounds prepared from left bracket **1**1C right bracket CH//3I seem to coexist with at least about 0. 2 mu mol of its non-radioactive form (carrier). In order to elucidate the source of the carrier, left bracket **1**1C right bracket CH//3I prepared under various conditions was converted into several **1**1C-compounds and their specific activities were measured by high performance liquid chromatography. Carbon contamination of LiAlH//4 was also examined by gas chromatography. It was shown that only a negligible amount of CO//2 was brought with the irradiated target N//2 gas and that the carrier amount decreased remarkably with the reduction of the amount and concentrations of the LiAlH//4-THF solution but not to less than 0. 2 mu mol. The use of Et//2O or Pr//2O instead of THF was found to give EtOH or PrOH, respectively, together with MeOH, all in small amounts. Hence, the 0. 2 mu mol carrier can be regarded as being originated in MeOH formed from a trace of THF remaining in the LiALH//4 after its drying step.