G. Bidoglio et al., HUMIC-ACID BINDING OF TRIVALENT TL AND CR STUDIED BY SYNCHRONOUS AND TIME-RESOLVED FLUORESCENCE, Environmental science & technology, 31(12), 1997, pp. 3536-3543
The complexation of Ti(III) and Cr(III) with groundwater humic acids (
HA) was investigated at pH 4.5 and pH 5.5 using different fluorescence
methods. These comprised both quenching measurements of the continuou
s and synchronous fluorescence of the HA ligand and and ion competitio
n method based on the time-resolved laser-induced fluorescence of HA-b
ound Eu(III). Modeling of the experimental data using an electrostatic
discrete site approach (Model V), yielded comparable values of intrin
sic binding constants for each of the studied metal, independently of
sample conditions (pH, metal:ligand ration) and fluorescence method us
ed. The results confirmed the validity of fluorescence techniques in t
he analysis of low concentration metal ion-HA interactions and indicat
ed that beside the aqua ion and the first hydroxc complex, other speci
es may also bind to humic acids.