Stability of binary complexes of L-aspartic acid in dioxan-water mixtures

Department of Inorganic & Analytical Chemistry, Andhra University, Visakhapatnam-530 003,

Andhra Pradesh, India

E-mail : gollapallinr@yahoo.com

Manuscript received online 07 December 2012, revised 24 January 2013, accepted 01 February 2013

An electrometric investigation was made on the formation equilibria of binary complexes of aspartic acid with Ca^II, Mg^II and Zn^II at 303 K and an ionic strength of 0.16 mol L^–1. The stability constants of the species ML, ML₂H₂, ML₂H₃, ML₂H₄ were refined with the computer program MINIQUAD75. The stability constants of Zn^II complexes were found to be greater than those of Ca^II and Mg^II due to pseudo inert gas configuration of Zn^II. The formation and distribution of different species were represented in the form of distribution diagrams. Influence of the co-solvent on the speciation was discussed based on the dielectric constant of the medium.