Studies on the reduction of [sup(99m)Tc]TcO4- by hydrochloric acid

The reduction of [sup(99m)Tc]TcO4- with HCl has been reanalyzed, using the chromatographic system originally proposed for this work by SHUKLA(5). The system utilized in this study consisted of a closed system that allowed heating without material or solution losses. At least two species (other than sup(99m)TcO4-) could be identified, whose Rsub(f) was either near the origin (low Rsub(f)) or near the front (high Rsub(f)). Following room temperature incubation, only TcO4- and the low Rsub(f) species could be observed, whereas following autoclaving for 30 min, no free TcO4- remained when HCl of 2 N concentration or higher was used. The high Rsub(f) species predominates at all HCl concentrations studied, and accounts for more than 90% of the sup(99m)Tc when HCl 5 N or higher was used. Electrophoretic studies also reveal the presence of two species in addition to TcO4-, one neutral and one cationic, which also can be observed in the generator eluted sup(99m)Tc. Although the HCl reduction of sup(99m)TcO4- appears to offer a simple method for obtaining a ''pure'' reduced technetium species, devoid of metals and other reducing agents, the present results and those of others do not allow us yet to unequivocally ascertain what is the oxidation state of technetium in the HCl reduction product(s). However, inasmuch as such species also appear to occur when sup(99m)TcO4- comes in contact with Cl- at acidic pH values, it is of interest that their identity and relevance in the formation of Tc complexes be ascertained. (author)