Stability constants and spectroscopic properties of thorium(IV)-arsenazo III complexes in perchloric acid

Abstract

The complexation of thorium with arsenazo III in perchloric acid was quantitatively investigated with ultraviolet–visible (UV–Vis) absorption spectroscopy. The UV–Vis absorption of both 1:1 and 1:2 (thorium to arsenazo III) complexes in perchloric acid were found to be highly enhanced than the previously reported absorption of the complexes in hydrochloric acid. The stability constants of thorium-arsenazo III complexes were determined via computational analysis, and the SIT (specific ion interaction theory) was employed to evaluate the dependence on ionic strength. This work contributes to a better understanding of the speciation and spectroscopic properties of thorium-arsenazo III complexes at high ionic strength.