Molecular Dynamics Simulation of the Effects of Mobile‐Phase Modification on Interactions in Reversed‐Phase Liquid Chromatography

Abstract

The effect of mobile phase composition (CH3OH/H2O) on the retention of solutes in RPLC was investigated by the molecular dynamics simulation method. A molecular model consisting of silica surface, solvent molecules, and a solute molecule was constructed. The conformation and the mobility of C18 ligands were characterized by the relative number density profiles of ligands, C1‐to‐C18 length distribution profiles, and the average mean squared displacement(MSD) of carbon atoms of ligands, respectively. The difference in all profiles due to a change in mobile phase composition is observed clearly, and the facts accord well with other spectroscopic and chromatographic data. The relative number density profiles of methanol and water molecules were constructed to characterize the distribution of solvent molecules around C18 ligands at each composition. With the increase of methanol content in the mobile phase, solvent molecules penetrate into the bonded phase, which shows the different solvation of the bonded stationary phase. The relative number density profiles of the solute (ethylbenzene) was used to see the distribution of the solute in the separation system. The calculated solute distribution is very consistent with the actual chromatographic retention behaviors.