Investigations on solute-solvent interactions of amino acids in aqueous solutions of sodium dihydrogen phosphate at different temperatures

The interactions of amino acids glycine, l-alanine and l-valine with sodium dihydrogen phosphate as a function of temperature have been investigated by the combination of volumetric and acoustic measurements. Densities and speeds of sound of amino acids in aqueous solutions of sodium dihydrogen phosphate have been measured at T = 288.15, 293.15, 298.15, 303.15 and 308.15 K and atmospheric pressure. The apparent molar volume (V (I center dot) ), the partial molar volume () and standard partial molar volumes of transfer () for amino acids from water to aqueous sodium dihydrogen phosphate solutions have been calculated from density data. Partial molar isentropic compression () and partial molar isentropic compression of transfer () have been calculated from speed of sound data. The pair and triplet interaction coefficients have been calculated from both the properties. The results have been explained based on competing patterns of interactions of co-solvents and the solute.