Reversed-phase HPLC of 99mTc methylene diphosphonate bone imaging kits with quantification of pertechnetate

Ion-pairing reversed-phase HPLC is used to separate a mixture of 99mTc methylene diphosphonate (MDP) complexes prepared by tin reduction of pertechnetate in the presence of ligand. Chromatographic conditions allow for the quantification of total pertechnetate concentration, as well as the determination of chemical purity of generator eluents from which 99mTc is derived. Both determinations can be made prior to actual labeling. Commercially available MDP kits from three manufacturers are evaluated. All three MDP kits, when labeled with 99mTc, produce multiple, chromatographically separable components. The formation of these Tc-MDP complexes is time dependent. The labeling procedure produces several products within the first 20 min, with up to fifteen complexes observed after 4 h. The results of this work demonstrate the presence of substantial chemical contamination in generator eluents.