Ko Taki

Production of no-carrier-added 11C-carbon disulfide and 11C-hydrogen cyanide by microwave discharge

Abstract No-carrier-added 11 CS 2 and H 11 CN were produced by microwave discharge with its conversion yield of about 9% for 11 CS 2 and of about 40% for H 11 CN in a 11 CO 2 /H 2 S/Ar and 11 CO 2 /H 2 N 2 system. Optimal conditions for batch production of each were established. About 56 mCi of 11 CS 2 with its specific activity of 42 mCi/μM within 14 min and about 200 mCi of H 11 CN with its specific activity of 198 mCi/μM within 20 min were shown to be obtained from 1 Ci of 11 CO 2 .

Reliability in determination of methanol concentration.

Two sampling methods for reliable determination of methanol concentration were studied. Methanol vapor stored in glass container was found to be decomposed on the glass surface. The decomposition increased as the surface area of the glass container was extended. The proportion of the decomposition in the glass container was relatively high, especially when the concentration of methanol vapor was low. Therefore, a reliable determination by the above sampling method was impossible. In the solid sorbent sampling by silica gel, the collected methanol was also decomposed, but the decomposed amount was negligibly small compared to the collected methanol when the amount of methanol was more than 0.1 microliter of the liquid methanol. It could be concluded from the foregoing findings that the determination of methanol concentration by this method is reliable.

Syntheses of selenium labelled compounds—II. The exchange reaction with elemental selenium

73Se labelled 2-selenouracil was prepared by the isotope exchange reaction method. It has been well known that in order to prepare labelled compounds in high specific activity by exchange reaction, the substrate compounds have to be used in small quantities. For 2-selenouracil, however, the reaction in low concentration is not always preferable for the labelling of high specific activity within a limited time. The optimum conditions for the preparation of [2-73Se]-2-selenouracil of maximum specific activity were determined.