Studies of the equilibria of complexes of Pr(III), Nd(III), Eu(III), Gd(III), Dy(III) and Er(III) with quercetin-5′-sulfonic acid in aqueous solutions

The equilibria Of the dissociation reaction of QSA as well as those of the complexation of QSA with Pr(III), Nd(III), Eu(III), Gd(III), Dy(III) and Er(III) in aqueous solutions were investigated. The composition and formation constants of the complexes were determined by the spectrophotometric and potentiometric methods. The spectrophotometric method was suggested to determine the above lanthanides with QSA.