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 B 1 (thiamine), vitamin B 3 (niacin) and Na 2 EDTA were potentiometrically studied, in aqueous media at the temperature of 37.0 ± 0.2 ⁰ C 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 B 1 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 B 1 revealed a remarkably high ability in forming mixed ligand complexes with all other four ligands. Results of this work clearly indicate that (EDTA-Vitamin B 1 ), (EDTA-Ascorbic), (Vitamin B 1 -Ascorbic), (Vitamin B 1 -Salicylic) and (Vitamin B 1 -Vitamin B 3 ) combinations can be used for detoxification of lead more effectively using dietary ligands.
Highlights
Today, lead (Pb) is considered as the most widely distributed toxic metal ion in the world due to many of its industrial applications (Das, 1990; Morose et al, 2008; Turner & Fader, 1962)
The present work was mainly undertaken to study the stability of mixed ligand complexes of EDTA with biologically significant molecules entering into our body via common drugs and food, as an attempt to introduce more effective and less toxic mixed ligand systems for the use in chelation therapy of Pb(II)
Variations in the pH values according to the volumes of alkali added are given in Figure 1 for a system, which formed a mixed ligand complex and in Figure 2 for a system which did not form a mixed complex, as two representatives
Summary
Lead (Pb) is considered as the most widely distributed toxic metal ion in the world due to many of its industrial applications (Das, 1990; Morose et al, 2008; Turner & Fader, 1962). The only way of curing lead toxicity is chelation therapy, which comes in two modes; single ligand and mixed ligand chelation therapy. This involves the formation of chelate complexes of toxic metal ions with administered drugs which can be excreted via urine or feces (Chisolm,1968; Goyer & Cherian, 1978; May and Williams, 1979; Bulman et al, 1979; Das, 1990;Wang et al.,2006). In order to have more reliable results, physiological conditions were applied during these experiments to study the aqueous
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