Spectrophotometric Studies For The Effect Of Pb+2 Ion On Some Chelators

Abstract

Lead is one of the toxic heavy metal when presented in a high level over it allowable limit. To detoxify this heavy metal a chelators were used as in a chelation therapy. This work studies the complexation of some chelators (EDTA and genistein) with Pb II ion. A spectrophotometric technique was applied in water and water-ethanol mixture as a solvent, at four different temperatures. A shift in it l_max and decrease in absorbance indicating the complex formation. The stoichiometry of these complexes were determined by a method of the continuous variation (Job's) method, it was found that Pb-EDTA were (1:2), Pb-gensitein (1:1). These chelator's have a high tendency to complex with Pb II ion which were reflected by its high values of their equilibrium constants. Thermodynamic parameters indicate a spontaneous interaction (negative free energy change DG), and the enthalpy changer for Pb-gensitein complex were positive and Pb-EDTA have negative DH which depends on type of the interaction and the structures of the complexes. The kinetic calculations shows a second order interaction.