Radiation‐induced tritium labelling and product analysis

By‐products formed in radiation‐induced tritium labelling are identified by co‐chromatography with authentic samples or by structure prediction using a quantitative structure‐retention index relationship. The by‐products, formed from labelling of steroids, polynuclear aromatic hydrocarbons, 7 ‐membered heterocyclic ring structures, 1,4‐benzodiazepines, 1‐haloalkanes, etc. with activated tritium and adsorbed tritium, are shown to be specifically labelled and anticipated products from known chemical reactions. From analyses of the by‐products, one can conclude that the hydrogen abstraction by tritium atoms and the substitution by tritium ions are the mechanisms of labelling. Classification of the tritium labelling methods, on the basis of the type of tritium reagent, clearly shows the active role played by tritium atoms and ions in radiation‐induced methods.