Effect of anionic micellar medium on thermo-acoustical parameters of aspartic acid and serine solutions

Abstract

Density and sound velocity data for aspartic acid and serine in water and in aqueous solution of anionic surfactant; Sodium dodecyl sulphate (SDS) were measured over a temperature range (303.15K–313.15K). Various volumetric and acoustical parameters including apparent molar volume (Φv), partial molar volume (Φvo), partial molar transfer volume, apparent molar isentropic compressibility (Φk), partial molar isentropic compressibility (Φok) and intermolecular free length (Lf) etc. for amino acid solutions in water and in aqueous surfactant (SDS) solutions were calculated from the measured data of density and sound velocity. The abovementioned calculated parameters have been used to explore the amino acid-surfactant interactions. Values of apparent molar volume are positive at all temperatures and are increasing with increasing temperature and amino acids concentrations. Similarly, intermolecular free length decreases with increasing amino acids concentrations both in water and aqueous surfactants solutions, which indicate strong intermolecular interactions in amino acids solutions. From results it is also obvious that due to the presence of resonance stabilization, aspartic acid interacts more strongly in both aqueous and SDS environment than serine.