Humic substances (HS) of different origins have been labeled with tritium by the thermal activation method. Specific radioactivity of labeled HS ( 3H-HS) was sufficiently high and varied from 0.14 to 0.6 TBq/g. Parent HS and 3H-HS were analyzed by size exclusion chromatography with radioactivity and UV detection. The results allowed concluding that (1) neither partial decomposition nor polymerization of HS occurred during labeling and (2) tritium labeled molecules have a regular distribution among HS fractions of different molecular weights. The performed correlation analysis revealed that there was no significant relationship between HS properties and specific radioactivity of the obtained 3H-HS. Thus universality of the developed technique for radioactive labeling of HS with tritium could be demonstrated.
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