The Determination of Charge of Anionic Tc-99m Radiopharmaceuticals

Abstract
The absolute charges on several anionic Tc-99m complexes were determined by an HPLC method using a SAX column and sodium sulphate as eluent. Retention times were measured over a range of [SO4 2-], and a non-linear regression technique was employed to determine complex charge. The system was validated using pertechnetate (-1) and the ligand TDG (-2). The charge of Tc-99m DTPA was shown to be -2. The major Tc-99m EHIDA complex has a charge of -1, while the main transient complex of this ligand has a -2 charge. Both of the complexes of Tc-99m TDG have a charge of -2. The method provided near integer values in all cases.