Sucrose dependence of solute inclusion in surfactant micelles: hydrophobic effect and geometrical considerations Original Research Article

In high performance liquid chromatography (HPLC) using a poly(octadecylsiloxane) as a stationary phase, a series of imidazole derivatives (IDs) as solutes, and a surfactant as a mobile phase modifier, a study on the surface tension of sugar on the inclusion of IDs in surfactant micelles was carried out by varying the salting out agent concentration. A mathematical treatment was developed to calculate the degree of inclusion, nc (the percentage of included guest solute) and the number of sucrose molecules excluded from the solute–micelle interface during the inclusion process. The thermodynamic parameters for solute inclusion processing the surfactant micelles were determined from Vant’Hoff plots. It was shown that the decrease in solute inclusion accompanying the sucrose concentration increase was principally governed by a decrease in the micelle radius due to the increased surface tension effects. This behavior caused a decrease in the hydrophobic interaction for ligand inclusion in the surfactant micelle explaining the observed thermodynamic trends.