Investigating thermodynamic, acoustic and spectroscopic parameters of rutin trihydrate with cationic surfactant CTAB in hydro-ethanolic solvent systems

Abstract

The research work represents thermodynamic, acoustic and spectroscopic analysis of a well known flavonoid; rutin trihydrate and cationic surfactant; cetyltrimethyl ammonium bromide (CTAB). The studies were conducted at five different temperatures (20 °C, 25 °C, 30 °C, 35 °C and 40 °C) and four different hydro-ethanolic concentrations (aqueous, 30% v/v, 70% v/v and absolute ethanol). The critical micelle concentration (CMC) values were obtained by studying the deviation in plots of specific conductivity (κ) with respect to change in CTAB concentration. These values were utilized to calculate various thermodynamic parameters viz. standard enthalpy change (ΔHom), standard entropy change (ΔSom) and standard Gibbs free energy change (ΔGom) of micellization. To further investigate the nature of interactions and flow properties; density (ρ), ultrasonic sound velocity (μ) and relative viscosity (ηr) of the system were measured. The obtained values were further used to calculate various acoustic parameters i.e. apparent molar volume (ϕv) and apparent molar compressibility (ϕk). Moreover, the FTIR and 1H NMR spectroscopic analysis was performed to confirm micelle formation and to determine the locus of flavonoid in micellar structure of surfactant. From the overall studies; electrostatic and hydrophobic interactions in the system were identified and enhanced flow properties were observed.