US EPA

3296679 

Journal Article 

Mixed ligand complex formation equilibria of some toxic metal ions with L-phenylalanine and maleic acid in CTAB-water mixtures 

Ramanaiah, M; Sailaja, BBV 

2014 

Yes 

Journal of the Indian Chemical Society
ISSN: 0019-4522 

SCIENTIFIC PUBL-INDIA 

JODHPUR 

91 

9 

1649-1660 

WOS:000350329900004 

The stability constants of ternary complexes of Pb-II, Cd-II and Hg-II ions with L-phenylalanine and maleic acid were determined pH metrically in the concentration range of 0.0-2.5% w/v cetyltrimethylammonium bromide (CTAB)water mixtures maintaining an ionic strength of 0.16 mol L-1 at 303.0 K. Alkalimetric titrations were carried out in different relative concentrations [M : L : X = 1.0 : 2.5 : 2.5, 1.0 : 2.5 : 5.0, 10 : 5.0 : 2.5] of metal (M) to L-phenylalanine (L) to maleic acid (X). Stability constants of ternary complexes were calculated and various models were refined with MINIQUAD75. The best fit chemical models were selected based on statistical parameters and residual analysis. The species detected are MLXH2, ML2XH2 and ML2XH for Pb-II and MLX2H3, ML2XH2 and ML2XH for Cd-II and ML2XH2, ML2XH and MLX2 for Hg-II. The relative stabilities of the mixed ligand complexes were compared with those of the binary complexes. The enhanced stability associated with the ternary complex is attributed to chelate effect, stacking interactions and hydrogen bonding. 

Stability constants; mixed-ligand complexes; L-phenylalanine; maleic acid; CTAB