ThermodynamicData for the Modeling of Lanthanoid(III)Sequestration by Reduced Glutathione in Aqueous Solution.

Thiscontribution reports the results of an investigation on thespeciation of various lanthanoid(III) cations (Ln3), namely,La3, Nd3, Sm3, Eu3, Gd3, Dy3, and Yb3, in the presenceof reduced glutathione (or simply glutathione, GSH), in NaCl(aq)at I= 0.15 mol·dm–3and T= 298.15 K. GSH forms in all cases the same four species,namely, Ln(GSH)H3, Ln(GSH)H2, Ln(GSH)H, andLn(GSH)OH, whose stability depends on the type of lanthanoid, althoughit is also possible to consider an average stability for a genericlanthanoid, at least for the protonated species. Measurements at differenttemperatures and ionic strengths for the La3ﱤ and Gd3ﱤ systems have also been performed, to evaluate theireffect on the speciation of both GSH and the Ln3熫抢.The dependence of the determined stability constants on Iand Thas been modeled by an extended Debye–Hückeltype and by the van’t Hoff equations. In this last case, theformation enthalpy changes of La3ﱤ species have alsobeen determined. The stability constants obtained have been thereforeused to quantify the sequestering ability of GSH toward the investigatedcations, in different pH, ionic strength, and temperature conditions,by the calculation of several pL0.5parameters. Their analysisshowed that, generally, the sequestering ability of GSH increaseswith increasing pH and decreases with increasing temperature, whilethe ionic strength has only a small effect. Finally, results obtainedmay be exploited for the evaluation of the speciation (and, therefore,of the sequestration) of any Ln3熫抢 in the presenceof GSH in different conditions of Tand I, like those featuring many natural waters and biological fluids. [ABSTRACT FROM AUTHOR]