Improved protein labeling by stannous tartrate reduction of pertechnetate

A procedure has been developed whereby small amounts of protein--specifically human serum albumin and immunoglobulin G--can be labeled with Tc-99m. Artifactual problems associated with electrolytic and stannous chloride labeling procedures are virtually eliminated. The procedure is satisfactory for labeling human serum albumin, normal goat immunoglobulin G, and goat anti-carcinoembryonic antigen immunoglobulin G.