Effect of Chemical and Radiochemical Impurities from Eluants on ^99mTc-Labeling Efficiency

Summary

Occasionally, radiopharmaceuticals prepared from the eluates of ⁹⁹Mo-^99m T c generators that have not been eluted for several days contain large amounts of free pertechnetate, as tested by radiochromatography and biologically by administration to patients. We find the most probable causes of poor ^99mTc-labeling in these cases to be:

a) the presence of a large concentration of ⁹⁹TcO₄ ^– in eluants;

b) insufficient stannous ions available for the complete reduction of Tc due to spontaneous oxidation of Sn in the vial and also due to oxidation of stannous ions by the presence of larger than expected concentrations of H₂O₂ and HO₂ radicals in the eluant.

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