Authors:

Abstract

Spectrophotometric and pH-metric studies of the aqueous binary and mixed ligand complexes of Pb(II), Cd(II), Al(III) and Cu(II) were carried out with ascorbic acid and paracetamol. The study was conducted at an ionic strength of 0.15 mol dm-3 and a temperature of 37.0 ± 0.2 oC. The protonation constants of the free ligands and the stability constants of the binary and mixed ligand complexes were determined using pH titration data. Proton dissociation of free ligands and complex formation were also qualitatively confirmed with UV data. The stabilities of mixed ligand complexes were quantitatively compared with those of the corresponding single ligand complexes in terms of Δlog K. Aluminium formed the most stable binary complex; Al (paracetamol)2, with a high overall stability constant (log β2 = 16.74). The stable mixed ligand complexes; Pb (ascorbic acid) (paracetamol), Cd (ascorbic acid)(paracetamol) and Cu (ascorbic acid) (paracetamol) were observed with positive Δlog K values showing the ability of using them in less harmful chelation therapy of these metals. Further, the results revealed that the bioavailability of both ligands will be lower for a metal intoxicated person.

J.Natn.Sci.Foundation Sri Lanka 2013 41 (4): 337-344

DOI: http://dx.doi.org/10.4038/jnsfsr.v41i4.6253

Keywords: Ascorbic acid, chelation therapy, mixed ligand complexes, paracetamol, stability constants, toxic metals