[en] The objectives of this year's research were to develop a method for rapidly determining TcO₄^- in ⁹⁹Mo//sup 99m/Tc generator eluates, to improve the ability to chromatographically determine individual Tc-HEDP complexes in radiopharmaceuticals, and to investigate the effects of TcO₄^- concentration and electrochemical reduction on the types and relative amounts of Tc-HEDP complexes present in a radiopharmaceutical formulation. A rapid and sensitive high performance liquid chromatographic (HPLC) method for the quantitative determination of pertechnetate (TcO₄^-) was developed. This HPLC-based analysis may be of considerable utility in assessing the history and function of ⁹⁹MO/sup 99m/Tc generators as well as in the routine analysis of reduced technetium radiopharmaceuticals for the presence of undesired TcO₄^-. Encouraging results were obtained on a dimethyl amine column using aqueous (NH₄)₂SO₄ as the mobile phase. The preparation of Tc(NaBH₄) HEDP radiopharmaceutical analogues using varying concentrations of total TcO₄^- shows a dramatic effect in the number and distribution of Tc-HEDP complexes over a TcO₄^- concentration range of 10^-2 to 10^-8M. These results suggest that total TcO₄^- concentration is an important parameter to be considered in the preparation of a specific Tc-HEDP complex to improve skeletal imaging. The preparation of Tc(electrode) HEDP radiopharmaceutical analogues by using electrochemical reduction was explored. The resulting solutions contain Tc-HEDP complexes that are tentatively identified as being the same complexes formed by NaBH₄ reduction, although the relative concentrations of these complexes are quite different with the two modes of reduction. Thus, electrochemical reduction shows promise as a viable route to the preparation of specific Tc-HEDP complexes for improved skeletal imaging