Analysis of ultraacoustic behavior of L-aspartic acid in aqueous sodium benzoate and ammonium acetate media

Acoustic study has been carried out on aqueous solutions of L-aspartic acid (ASP) in presence of two food additives sodium benzoate (SB) and ammonium acetate (AA) at 298.15 K. Propagation of ultrasonic sound wave passing through the experimental solutions bears a direct relation with various weak and strong molecular interactions acting between components of the solution. Isentropic compressibility (Ks), appar-ent molar isentropic compressibility (Ks;/) and isothermal compressibility (KT) decrease with increasing electrostriction of water molecules surrounding the solute and cosolute ions. Although ion-solvent inter-actions are predominant, reasonable extent of ion-ion, ion/hydrophilic-hydrophilic and ion/hydrophobic-hydrophobic interactions also exists between different segments of solute and cosolute ions. In the pro-cess of solvation and ion association reformation of water structure takes place. Various parameters like molar free length (Lf), molar free volume (Vf), relative association (RA), internal pressure (pi), acoustic impedance (Z) and surface tension (y)derived from density (q), viscosity (g) and ultrasonic velocity (U) advocate for stronger ion-solvent interactions, ion-pair formation and structure building ability of ASP in presence of SB/AA.(c) 2023 Elsevier B.V. All rights reserved.