Synthesis, purification, storage and isotopic analysis of CT4 on the multicurie scale

Multicurie amounts of CT 4 were prepared from T 2 via a twosteps synthesis with an overall yield of ca. 75%. After purification, the radio gas chromatographic analysis of the product revealed only a 0.5% T2 (or HT) impurity. The isotopic analysis, carried out independently by mass spectrometry and by high‐resolution gas chromatography, showed that, immediately after preparation, tritiated methane aontained over 97.8 mol% CT4, with only traces of particular tritiated methanes. However self radiolysis, in particular fast intermolecular H/T scrambling, caused severe storage problems. Even after dilution with a thousand‐fold exaess of CH4, radiation‐induced isotopic exahanges led to serious contamination of CT4 by partially tritiated methanes. A dramatic improvement was obtained, without further dilution of CT4, by addition of 1 ‐ 2 mol% NH3, which completely suppressed radiolytic H/T scrambling. A preparative gas chromatographic technique was developed, which allows isolation of CT4 in a state of high radiochemical and isotopic purity.