Investigation on molecular interaction of amino acids in aqueous disodium hydrogen phosphate solutions with reference to volumetric and compressibility measurements

• Densities and speeds of sound of amino acids in aqueous disodium hydrogen phosphate.
• Partial molar volumes and compressibility of transfer.
• Positive values of transfer volume indicates interactions between ions of amino acids and TSC.
• Ion–hydrophilic and hydrophilic–hydrophilic interactions are present.
• Pair-wise interactions are dominant in the mixtures.

The interactions of amino acids glycine (Gly), l-alanine (Ala), and l-valine (Val) with disodium hydrogen phosphate (DSHP) as a function of temperature have been investigated by combination of volumetric and acoustic measurements. Densities (ρ) and speeds of sound (u) of amino acids in aqueous solutions of disodium hydrogen 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 (Vϕ), the partial molar volume (Vϕ0) and standard partial molar volumes of transfer (ΔVϕ0) for amino acids from water to aqueous disodium hydrogen phosphate solutions have been calculated from density data. Partial molar adiabatic compressibility (κϕ,s) and partial molar adiabatic compressibility of transfer (Δκϕ,S0) have been calculated from speed of sound data. The pair (VAB, κAB) and triplet (VABB, κABB) interaction coefficient have been calculated from both the properties. The results have been explained based on competing patterns of interactions of co-solvents and the solute.

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