Chemical Speciation of Binary Complexes of Pb(Ii), Cd(Ii) and Hg(Ii) with L-Methionine in Propylene Glycol -Water Mixture

Chemical speciation of Pb (II), Cd (II) and Hg (II) complexes of L-methionine in 0.0-60.0 % v/v propylene glycol-water mixtures has been studied pH metrically maintaining an ionic strength of 0.16 M at 303 K. The active forms of ligand are LH3 +, LH2 and LH. The predominant species detected are MLH, ML and ML2. Models containing different numbers of species were refined by using the computer program MINIQUAD75. The bestfit chemical models were arrived at based on statistical parameters. The trend in variation of complex stability constants with change in the dielectric constant of the medium is explained on the basis of electrostatic and non-electrostatic forces.