Radioactive labelled, self-decomposition

Labeled compounds experience self-radiolysis induced by the radioactive decay. The extent of such radiation effects depends on the half-life, the decay energy, the specific activity of the sample, and the G-value for decomposition. The presence of other substances can considerably affect the amoimt of damage. Aromatic compounds such as benzene (as a solvent) can serve as a protective medium to minimize radiation self-decomposition, whereas water or oxygen enhance it. 

Radiochemical purity. The radiochemical purity is the fraction of the stated radioactive nuclide present in the stated chemical form. For tracers of elements stabilized in two or more oxidation states, it is necessary to check their oxidation state by their chemical behavior, ion exchange for example, preferably just before the experiment. In organic compounds labeled with a radioactive nuclide, it is desirable that the number and position of labeling of the radioactive nuclide are unique. However, when the number and position of the nuclide in a compound do not essentially affect its chemical behavior as is often the case in tritium-labeled ones, use of a mixture of a compound labeled with different number of the stated nuclide or labeled at different positions is acceptable. The purity of some labeled compounds decreases gradually due to oxidation, self- or radiolytic decomposition during long storage. Such a labeled compound should be assayed and purified, if necessary, before use. 

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