Evaluation of the complexation behavior between humic acid and UO22+with fluorescence spectroscopy and its mixture analysis

Abstract

SummaryThe fluorescence of humic acid (HA) is quenched due to its complexation with UO22+ions, leading to the evolutionary quenched intensity profile (quenching profile) as a function of UO22+concentration. This quenching behavior was investigated using 3-dimensional (3D) and synchronous (SyF) fluorescence spectroscopy. The quenching profile obtained by means of SyF spectroscopy was deconvoluted by SIMPLISMA, which is an interactive self-modeling mixture analysis method. Two sites, which contribute to the fluorescence of HA and whose fluorescence is quenched due to its complexation with UO22+, have been extracted, and the quenching profile was resolved to the fluorescence intensity profiles of these sites and the corresponding spectra. Based on these intensity profiles, the apparent stability constant (logKapp) and the concentration of site (CL) were evaluated for each site, using nonlinear least-squares regression to the Multisite Ryan-Weber Model.