A bonded phase material useful with a chromatographic separation process. The bonded phase material includes a hydroxyl bearing porous material, a first controlled stoichiometric amount of a first interactive silane covalently bonded to the surface of the hydroxyl bearing porous material and at least one additional interactive silane covalently bonded to the surface of the hydroxyl bearing porous material to provide the porous material with a gradient of functionality of varied polarity creates a unique overall polarity which is not obtainable by the separate interactive silanes themselves. The method of silating the porous material includes sequential application of controlled stoichiometric amounts of the interactive silanes.