Viscometric and spectroscopic studies on interactions of glycine with aqueous buffer solutions

Abstract

Abstract To study the solvation and hydration behavior of glycine, viscosity measurements have been carried out for glycine in water of pH = (1.00, 7.40 and 14.00) and in different concentrations (0.1, 0.5 and 1.0) M of aqueous potassium/sodium phosphate buffer (KPB/NaPB) solutions of pH = (1.00, 7.40 and 14.00) at different temperatures, T = (298.15, 308.15, 310.15 and 318.15) K. Viscosity B-coefficients for glycine in water and in aqueous buffer solutions have been obtained at different temperatures using Jones-Dole equation. Viscosity B-coefficients of transfer (∆trB) values have been calculated from viscosity B-coefficient data. Both positive and negative viscosity B-coefficients of transfer have been observed in the studied system. The Gibbs energies of activation for viscous flow per mole of solvent (∆μ1o) and per mole of solute (∆μ2o) have been calculated and discussed in terms of transition state theory. Solvation (Sn) and hydration (nH) numbers have also been calculated from these data. The results have been discussed in terms of solute-solvent and solute-solute interactions in these systems. The structure-making/breaking ability of glycine has been discussed in terms of the sign of dB/dT. UV absorption spectra for glycine in aqueous KPB solutions has been recorded. All the viscometric and spectroscopic parameters have been used to explore various interactions that may arise in presently investigated ternary solutions.