Chemical Speciation Of Complexes Of Maleic Acid And L-Phenylalanine With Toxic Metal Ions In Dimethylformamide-Water Mixture

Abstract

The protonation equilibria of L-phenylalanine and maleic acid and the formation of binary complexes of Pb (II), Cd (II), and Hg (II) with L-phenylalanine and maleic acid were investigated pH metrically in Dimethyl formamide-water mixtures (0-50%v/v) at 303 K and ionic strength of 0.16 mol dm-3 separately. The protonation constants and stability constants have been calculated using the computer program MINIQUAD75 and the best fit models are arrived at based on statistical grounds employing crystallographic R factor, χ2, skewness and kurtosis. The dominant species refined were ML2, ML2H, and ML3 of F and MA complexes of Pb(II),Cd(II) and Hg(II) in DMF-water mixtures. The appropriateness of the experimental conditions was verified by introducing errors deliberately. The trend in variation of protonation constants and stability constant of the complexes with dielectric constant of the medium was attributed for the formation and possible structures of the complex species presented. The chemical speciation was explained based on the distribution diagrams drawn using HYSS HYPERQUAD suite program.