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Spectrophotometric studies for the interaction of Pb+2 ion with some chelators

ElhamM.Al-Rufaie, FahadD.Fahad

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 (penicillamine and quercetin) with Pb II ion. A spectrophotometric techniques were applied in water and water-ethanol mixture as a solvent, at four different temperature. A shift in it 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-quercetin (1:1), and Pb-penicillamine (2:1). 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 Go), and the enthalpy changer have negative Ho which depends on type of the interaction and the structures of the complexes. The kinetic calculations shows a second order interaction.