Abstract
The oxidation state of technetium in several radiopharmaceutical preparations was investigated by forming uncharged complexes of known valence and high stability, followed by extraction into chloroform. Successful extractions by 8-hydroxyquinoline (oxine) which forms a Tc(V) uncharged complex, showed that SnCl 2-reduced Tc-gluconate, citrate, and mannitol complexes at 2 × 10 −9 M concentration were Tc(V) compounds. Extractions by diphenylcarbazone showed that Tc-pyrophosphate and Tc-HEDP complexes were Tc(IV) or perhaps Tc(III). By means of oxine extraction, it was found that the reaction of pertechnetate with SnCl 2 solutions, produced mostly Tc(V) in diluted pertechnetate and SnCl 2 solutions, but further reduction was observed as the SnCl 2 concentration was raised. A reported displacement of Tc-pyrophosphate and Tc-HEDP by Na-gluconate and displacement of Tc-DTPA by cyclam in alkaline solution was shown to involve oxidation, probably by traces of air. The Tc-DMSA complex produced by SnCl 2 reduction contains some Tc(IV), but the problem is complicated by the existence of four or more compounds. Diphenylcarbazone is not an ideal extractant because the chemistry of its reaction with Tc is not understood, and it is not as efective in extracting Tc(IV) as oxine is for Tc(V).
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