Thermodynamic Data for the Modeling of Lanthanoid(III) Sequestration by Reduced Glutathione in Aqueous Solution

Abstract

This contribution reports the results of an investigation on the speciation of various lanthanoid(III) cations (Ln3+), namely, La3+, Nd3+, Sm3+, Eu3+, Gd3+, Dy3+, and Yb3+, in the presence of reduced glutathione (or simply glutathione, GSH), in NaCl(aq) at I = 0.15 mol·dm–3 and T = 298.15 K. GSH forms in all cases the same four species, namely, Ln(GSH)H3, Ln(GSH)H2, Ln(GSH)H, and Ln(GSH)OH, whose stability depends on the type of lanthanoid, although it is also possible to consider an average stability for a generic lanthanoid, at least for the protonated species. Measurements at different temperatures and ionic strengths for the La3+/GSH and Gd3+/GSH systems have also been performed, to evaluate their effect on the speciation of both GSH and the Ln3+ cations. The dependence of the determined stability constants on I and T has been modeled by an extended Debye–Huckel type and by the van’t Hoff equations. In this last case, the formation enthalpy changes of La3+/GSH species have also been determined. The st...