Complexation and solvent extraction behaviour towards lanthanide ions with quercetin

Abstract

The complexation behaviour towards lanthanide (Ln) ions with quercetin (Q) was evaluated both in homogeneous phase and in liquid-liquid extraction process. As confirmed by UV–vis, fluorescence techniques and 1H NMR titration, Q can bind lanthanide ions through 4‑carbonyl and 3-hydroxyl of ring C with the stoichiometric ratio of 2:1 (Q:metal) in methanol solution. The binding constants for Q and Eu(III) (K1 = (3.87 ± 0.20) × 104 M−1, K2 = (2.56 ± 0.15) × 103 M−1) are slightly higher than that of Q-La(III) (K1 = (2.01 ± 0.15) × 104 M−1, K2 = (1.53 ± 0.12) × 103 M−1) and Q-Yb(III) (K1 = (1.73 ± 0.12) × 104 M−1, K2 = (1.25 ± 0.22) × 103 M−1). Solvent extraction revealed that the extractability of Ln(III) was relevant to the acidity and salinity of aqueous phase and extraction efficiency was Eu(III) > La(III) > Yb(III) at the same acidity.