Speciation of binary complexes of Co(II), Ni(II), Cu(II) and Zn(II) with L-aspartic acid in anionic, cationic and neutral micellar medium

Abstract

Chemical speciation of binary complexes of Co(II), Ni(II), Cu(II) and Zn(II) with L-aspartic acid was investigated pH-metrically in (0.5 -2.5%) anionic, cationic and neutral micellar media. The stability constants were calculated using the computer program MINIQUAD75. The best-fit chemical models were selected based on statistical parameters and residual analysis. The models for the binary species contained MLH, ML 2 and ML 2 H for Co(II), ML, MLH, ML 2 for Ni(II) and Cu(II), ML 2 , ML 2 H and ML 2 H 2 for Zn(II) in anionic, cationic and nonionic micellar media The trend in variation of stability constants with change in the mole fraction of the medium was explained on the basis of electrostatic and nonelectrostatic forces. Distributions of the species with pH at different composition of micellar media were also presented.