Study on mixed ligand complexes of Pb(II) with EDTA and dietary ligands to investigate the applicability on chelation therapy

Abstract

Lead is the most distributed toxic metal in the world and chelation therapy is a remedy for removing it from the body, if a person is intoxicated. Stability constants of both binary and mixed ligand complexes of Pb(II) with salicylic acid, ascorbic acid, vitamin B1(thiamine), vitamin B3 (niacin) and Na2EDTA were potentiometrically studied, in aqueous media at the temperature of 37.0 ± 0.2 ⁰C and the ionic strength of 0.15 mol dm-3 in order to identify better mixed ligand systems suitable for chelation therapy of lead. Both metal-ligand and proton-ligand formation constants were calculated using Irving-Rossotti equations. The Formation of ternary complexes was further confirmed theoretically by plotting composite curves. Δ log K values calculated revealed that all mixed complexes were more stable than the complexes of corresponding binary systems. EDTA-Vitamin B1 and EDTA-Ascorbic mixed complexes with Pb(II) disclosed very high stability constants, which were two times greater than that of EDTA binary complex. Vitamin B1 revealed a remarkably high ability in forming mixed ligand complexes with all other four ligands. Results of this work clearly indicate that (EDTA-Vitamin B1), (EDTA-Ascorbic), (Vitamin B1-Ascorbic), (Vitamin B1-Salicylic) and (Vitamin B1-Vitamin B3) combinations can be used for detoxification of lead more effectively using dietary ligands.

Keywords

• stability constants, in vitro conditions, chelation therapy, thiamine, niacin, vitamin c, salicylic acid