Modeling solvation on the chemically modified silica surfaces.

A detailed molecular-level description of the retention mechanism in RP-HPLC is a point of great interest to analytical chemists. For this purpose, the solvent adsorption on the octadecyl stationary-bonded phase was investigated. Preferential adsorption of solvents from the acetonitrile-water mobile phase was modeled on the silica surface with one, two, three and four organic ligands, which represents a series of non-end-capped-bonded phases with different coverage density of bonded ligands. As a result of the computer simulation, the increase of adsorbed acetonitrile around bonded ligands is observed. The number of water molecules near the modeled surface is observed as well. The results are in agreement with experimental measurement of acetonitrile excess adsorption isotherms on the series of in-house made stationary-bonded phase.