Apparent molar volume, compressibility, and spectroscopic studies of ionic surfactants in aqueous solutions of antibiotic gemifloxacin

Abstract

This work aims to explore the interactions between a wide-spectrum bactericidal drug, gemifloxacin (GMF), and micelles of cationic (dodecyltrimethylammonium bromide, DTAB) and anionic (sodium dodecyl sulfate, SDS) surfactants at the molecular level under physiological conditions (using a phosphate buffer, pH 7.4). Various physical parameters are calculated from volumetric and acoustic data. These include apparent molar volume (), apparent molar isentropic compressibility (), isentropic compressibility (), specific acoustic impedance (Z), relative association (RA), intermolecular free length (Lf ) and sound velocity number (U). The obtained quantities are interpreted regarding of solute-solute and solute-solvent interactions employing the cosphere overlap model and electrostriction effect. Further, normal and differential UV-visible spectroscopy is employed to predict GMF locus in ionic micelles and to find the binding constant (Kb ) and partition coefficient (Kc ) along with the corresponding free energy changes of GMF-ionic micelle systems. The results demonstrate that the binding and partitioning of GMF with SDS is more significant than DTAB.