Abstract
Abstract The chemistry of a purple complex which is formed in the course of the preparation of 99 m Tc-human serum albumin as a radiopharmaceutical for diagonosis was studied. This compound which is characterized as a unhydrolysed ferric ascorbate complex is assumed to be produced from ferrous ion and ascorbic acid through the formation of ferrous ascorbate (1:1) complex with the participation of molecular oxygen. The present results suggest that, independently of the reaction with molecular oxygen, the ferrous ascorbate complex reacts with 99 m TcO 4 − to form a reduced 99 m Tc species, which is then incorporated into human serum albumin. At the same time, the purple ferric complex was found to form a stable complex with 99 m Tc. Thus the presence of ferric complex is unfavorable for the labelling of human serum albumin with 99 m Tc. The high labelling efficiency was achieved by the labelling procedure under nitrogen atmosphere in the presence of deferoxamine which coordinates selectively with ferric ion with an extremely high stability constant.
Published Version
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