RADIOCHEMICAL PURITY AND MOLAR ACTIVITY OF COMPOUNDS LABELED WITH SHORT-LIVED RADIOISOTOPES

A molecule containing n radioactive atoms is assumed to form a cascade of impurities if any of them decays. A mathematical model of the molecular decay process of compounds labelled with short-lived isotopes is proposed. Equations are derived for the change of radiochemical purity and specific activity with time. Progesterone labelled with 1, 2, 4, and 6 tritium atoms agrees satisfactorily with the experimental and calculated radiochemical purities. The molecular decay of compounds labelled with short-lived isotopes in contrast with radiolysis does not depend on the storage conditions and is a fundamental property of this class of compounds.