Rapid assay for total unbound Tc-99m in preparations of Tc-99m in macroaggregated albumin: concise communication.

A rapid economic filter-paper assay for determining total unbound Tc-99m in preparations of Tc-99m macroaggregated albumin (Tc-99m MAA) is described. The procedure uses Whatman 542 filter-papter discs and aqueous 0.009% NaCl as wash solution. The principal radiochemical impurities found in Tc-99m MAA kits are not significantly adsorbed to the filter matrix. The procedure can be completed in 1--2 min and gives results comparable to those obtained by the centrifuge assay (USP XIX).