Electrophoretic determination of charge on carrier‐free ^99mTc‐labeled complexes

A new method for determining the charge on carrier‐free ^99mTc‐labeled complexes is described. This method and mixed‐ligand experiments were used to determine if the charge on the technetium 99m complex of N‐(2,6‐dimethylphenylcarbamoylmethyl)iminodiacetic acid (I) is ‐1 and if the ligand to technetium ratio in the complex is 2:1. The preparation of an iodinated analog (II) of I and its ^99mTc‐labeled complex is described, as is the biodistribution of the ^99mTc‐labeled complex in mice. The syntheses of the ⁵¹Cr(III)‐ and ⁵⁷Co(III)‐labeled complexes also are described. The net biliary excretion in mice of both the ^99mTc‐ and ⁵¹Cr‐labeled complexes of II was significantly greater than that of the ^99mTc‐labeled complex of I.