[Labeling of steroids with tritium]

Conditions have been elaborated for the tritium labeling of some steroids to a molar activity of the order of 1 TBk/mol by heterogeneous catalytic isotopic exchange. For steroids without a keto group, isotopic exchange with gaseous tritium is most effective in neutral solvents, whereas for steroids with a keto group an alkaline medium is preferable. At certain pH values it was possible to void hydrogenation of the double bonds in the compounds.