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The acid-base equilibrium of 1,10-phenanthroline (1,10-phen) in the presence of polyethylene glycol 400 (PEG-400, non-ionic) and tetrabutylammonium bromide (TBAB, ionic) micellar media has been studied by Calvin-Wilson titration technique at different mole fractions (0.5%-2.5%) of PEG-400 and TBAB micellar solutions at an ionic strength of 0.16 mol dm −3 NaCl and at a temperature of 298 K. The pH metric data were subjected to SCPHD program to obtain correction factor and K w which were given as initial inputs for MINIQUAD75 program to refine protonation constants. HySS program was then used to generate the species distribution diagrams versus pH using the results obtained from the MINIQUAD75 program and SIM run data. The difference in values of protonation constants in aqueous medium (logβ 1 = 4.93 & logβ 2 = 6.22) and in the micellar media (PEG-400, logβ 1 = 4.89 & logβ 2 = 5.91 and TBAB, logβ 1 = 4.84 & logβ 2 = 5.73) is attributed to different intrinsic solvent characteristics of micelles. In case of ionic surfactants, the electrostatic micellar surface is an additional contributing factor.

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Investigation of mononuclear complex of L-ornithine in tetrabutylammonium bromide (TBAB, a cationinc surfactant) micelle media has been made pH metrically at constant temperature and ionic strength in different percentage of micellar solutions (0.0-2.5 %). Stability constants and best fit model for metal complexes were obtained by MINIQUAD75 computer program on the basis of the analysis of residues and other statistical parameters. Accordingly, ML, ML2, MLH and ML2H for both Co(II) and Cu(II) and ML2 and ML2H for Ni(II) mononuclear chemical models were obtained. The stabilization/destabilization equilibria of the binary system for the model species with percentage composition of micelles at constant ionic strength and temperature could be attributed to dielectric constant and other intrinsic interaction properties of tetrabutylammonium bromide micelle with ligands and metal ions. The plot of percentage of species against pH values has been generated from SIM refined data using origin85 software.