POTENTIOMETRIC STUDY ON THE COMPLEXATION EQUILIBRIA OF SOME RARE-EARTH IONS WITH GLUTAMINE

Solution equilibria for La(III), Nd(III), Eu(III), Gd(III), Yb(III) and Lu(III) with glutamine have been studied, potentiometrically in aqueous medium at different ionic strength and temperatures. Method of Irving-Rossotti and its modifications have been employed to calculate the value of the formation constants and overall stability constants for these complexes. The thermodynamic parameters of the complexation process under the experimental conditions have been evaluated, the stability sequence for 1:2 (metal ion: ligand) complexes was found to be: Lu(III) > Yb(III) > Eu(III) > Gd(III) > Nd(III) > La(III). Effect of ionic strength, temperature and the nature of the central metal ion on the stability constants of the complexes were discussed.