HPLC analysis of Tc-99m iminodiacetate hepatobiliary agents and a question of multiple peaks: concise communication

The application of high-performance liquid chromatography (HPLC) to Tc-99m-labeled iminodiacetate hepatobiliary agents is described. The method is sensitive to variations of phenyl ring structure and give different retention times for the different agents. Technetium-99m-labeled N-(2, 6-diethylacetanilide)iminodiacetate from different sources had two components in differing amounts. It was determined that the second component, which is minor at pH above 6, is major when prepared at pH 4.5 or less. Raising the pH results in rapid conversion of the second component into the first. This observation was demonstrated also in plasma and would be expected to occur when the radiopharmaceutical is injected intravenously. The kinetics of appearance of the preparations in the bile when prepared at pH 4 and pH 6 were essentially the same.