Characterization of tin-technetium colloid in technetium-labeled albumin preparations.

The Tc-99m human serum albumin (HSA) system has been reinvestigated with gel filtration as the assay method. Other than Tc-99m HSA, two radioactive components have been isolated by this technique. Both components are tin-technetium colloids of differing particle sizes, and the relative quantity of each one is pH-dependent. The colloid has been further characterized by protein-induced x-ray emission analysis (PIXE) and by tissue distribution in rats. By this gel-filtration method, commercial Tc-99m HSA kits have been evaluated and have revealed varying amounts of colloids present.