ICES studies on 99mTc-halide complexes: Formation, hydrolysis and ligand exchange

Abstract

The Internal Conversion Electron Spectroscopy (ICES) method was employed to study the products of reduction of no-carrier-added [ 99mTc]pertechnetate by concentrated hydrochloric, hydrobromic and hydroiodic acids. The reductions were carried out in vacuum with subsequent evaporation of the solution to dryness. In the solid deposits, containing ∼ 10 −9g Tc, chemical shifts of 99 m Tc 3 d 5 2 electron binding energies were measured and the results were compared with known data of x-ray photoelectron spectroscopy for defined technetium compounds. It was evidenced that all reduction/evaporation procedures yielded 99mTc(IV)-halide complexes. Another technique of reduction by vapours of halogen acids was proposed to prepare thin radioactive sources for physics studies. The reduction power of alkali halides in absence of acids was examined and a partial reduction of pertechnetate by iodide was found. The product was a hydrolysed species. The hydrolysis of halide complexes yielded the same product. In the absence of acids, dissolved species were partly oxidised to Tc(VII) by air. Oxidation was most apparent for the chloride and negligible for the iodide system. Ligand exchange of chloro and bromo complexes to chelate with DTPA at pH 3 was found to be uncomplete. Tc(IV) hydrolysed species, Tc(IV)DTPA and Tc(VII) were evidenced. Tc(V)DTPA was also observed which arises from partially oxidised products.