Chemical Speciation of Complexes of L-phenylalanine and maleic acid with toxic metal ions in Dimethylformamide -Water Mixtures
Wakgari Bungula Negessa, Wondimu Tesfa Tefera, Tegene Desalegn Zeleke and Hadgu Haliekiros Belay*
Department of Applied Chemistry, Adama Science and Technology University, Adama, Oromia, Ethiopia.
E-mail: hadgu10@gmail.com
ABSTRACT
The formation equilibria of 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 moldm-3. The dominant species detected were ML2, ML2H, and ML3 of LPA and MA complexes of Pb(II), Cd(II) and Hg(II) were refined in DMF-water mixtures. The appropriateness of the experimental conditions was verified by introducing errors deliberately. The models containing different numbers of species were refined by using the computer program MINIQUAD75. Selection of the best fit models was based on the statistical parameters. The trend in variation of 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.
Keywords: speciation, complex equilibria, Dimethyl formamide, L-phenylalanine, maleic acid,
stability constants, HYSS HYPERQUAD, MINIQUAD75
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