Equilibrium studies of binary and ternary complexes involving tricine and some selected α-amino acids

The formation equilibria for the binary complexes of Co-II, Ni-II, Cu-II, Zn-II, Cd-II, Mn-II, Pb-II, Th-IV, UO2II, and Ce-III with tricine and for the ternary complexes involving some alpha-amino acids (glycine, alpha-alanine, proline, serine, asparagine, and aspartic acid) were investigated using pH-metric technique. The formation of binary and ternary complexes was inferred from the pH-metric titration curves. It was deduced that tricine acts as a primary ligand in the ternary complexes involving the monocarboxylic amino acids (glycine, alpha-alanine, proline, serine, and asparagine), whereas it behaves as a secondary ligand in the ternary systems containing the dicarboxylic aspartic acid. The ternary complex formation was found to take place in a stepwise manner. The stability constants of the complexes formed in aqueous solutions were determined potentiometrically under the experimental conditions (t=25degreesC, I=0.1 mol dm(-3) NaNO3). The order of stability of the ternary complexes in terms of the nature of the amino acids is investigated and discussed. The values of Deltalog K for the ternary complexes have been evaluated and discussed. Evaluation of the effects of ionic strength and temperature of the medium on the stability of the ternary system M-II-tricine-alpha-alanine (M-II=Co-II, Ni-II, and Cu-II) has been studied. The thermodynamic parameters were calculated and discussed.