Volumetric and Acoustic Characteristics of Potassium Sorbate with L-ascorbic Acid and Ascorbyl Glucoside: A Thermodynamic Study

Abstract

The stability, safety, and shelf life of various formulations are significantly enhanced by the incorporation of antioxidants and antimicrobial preservatives. This work investigates the molecular interactions and thermodynamic characteristics of ternary mixtures consisting of L-ascorbic acid/Ascorbyl glucoside in aqueous solutions of Potassium sorbate, at temperatures ranging from 288.15 K to 318.15 K and concentrations from (0.0 to 0.7) mol·kg⁻¹. Experimental measurements of density and ultrasonic velocity were used to calculate key thermodynamic parameters, including partial molar volumes (\(V_{\upphi }^{0}\)), apparent molar volume \(({V}_{\phi }\)), isentropic compression \({(K}_{\phi ,s}\)), and their transfer parameters (\(V_{\upphi }^{0}\), \(\Delta K_{\upphi }^{0}\)). The results reveal stronger solute -solvent interactions for Ascorbyl glucoside compared to L-ascorbic acid. Additionally, the analysis of relative association (R_a), relaxation strength (r_s) and specific heat ratio (ϒ) provides further insights into the molecular behavior and structural dynamics of these mixtures. The co-sphere overlap theory provides a quantitative framework for interpreting molecular interactions, assessing whether ternary mixtures promote structural organization or disruption. Temperature-dependent behavior is analyzed through the first derivative (\(\partial {\text{E}}_{\upphi }^{0}/\partial \text{T})\) _P, offering insights relevant to applications in the cosmetics, chemical, and pharmaceutical industries.