An investigation of the effect of the quantity of stannous ion on the quality of technetium‐99m labelled albumin

Abstract The importance of maintaining a low ratio of stannous ion to albumin molecules in order to obtain a high quality technetium‐99m labelled albumin is demonstrated. It is further shown that the direct preparation of technetium‐99m albumin by reduction of the technetium‐99mm pertechnetate with stannous ion inevitably leads to the contamination of the product with a certain amount of tin colloid which is also labelled with technetium‐99m. It is demonstrated that this can be avoided by utilizing labelling techniques involving the initial formation of other technetium chelates which are less stable than the albumin complex under certain conditions, adding the albumin to that preparation, adjusting the conditions and thus allowing the albumin to become labelled with technetium‐99m via an exchange with the original chelating agent.