CHEMICAL SPECIATION OF BINARY COMPLEX OF ETHYLENEDIAMINE WITH COBALT (II) AND ZINC (II) IN SODIUM DODECYL SULFATE

Abstract

Chemical speciation of binary complexes of Co(II), and Zn(II) with ethylenediamine was studied pH– metrically in various concentrations (0-2.5% v/v) of SDS-water mixtures maintaining an ionic strength of 0.12molL-1 (NaCl) at 298.0 K. SDS is used to mimic the low dielectric constant at the active site cavities in bioactive molecules like enzymes and proteins. The active forms of the ligand were LH22+, LH+, and L. Alkalimetric titrations were carried out in different relative concentrations (M: L = 1:1, 1:2, 1:3) of metal (M) to ethylenediamine (L) with sodium hydroxide as titrant. The predominant species detected for Co(II) and Zn(II) were ML (at pH 4.5 to 7.5), ML2 (at pH 6.5 to 9.0) and ML3(at pH 9 and above) .The models containing different numbers of species were refined by using MINIQUAD75 algorism. The best-fit chemical models that represent the experimental data were arrived at based on statistical parameters like, sum of square of the residuals,X2, R-factor, skewness and kurtosis. The trend in variation of stability constant (log ) is due to increases in the concentration of surfactants. Effect of errors in the ingredients on the values of stability constants was also studied. The species distribution diagrams with pH at different compositions of SDS were also presented. The most probable structures of plausible binary complexes were suggested in the study