Determination of the solvent density profiles across mesopores of silica-C18 bonded phases in contact with acetonitrile/water mixtures: A semi-empirical approach

The results show that C18 chains are mostly solvated by acetonitrile molecules, water is excluded from the C18-bonded layer, and acetonitrile concentrates across a 15-25 Åthick interface region between the C18 layer and the bulk phase. These actual density profiles are expected to have a direct impact on the retention behaviour of charged, polar, and neutral analytes in RPLC. They also provide clues to predict the local mobility of analytes inside the pores and a sound physico-chemical description of the phenomenon of surface diffusion observed in RPLC.