In an apparatus for liquid chromatography the improvement which comprises a chromatographic column packed with a solid packing material comprising porous silica gel particles, having a specific surface area of 5 to 1500 m.sup.2 /g, an average pore diameter of 20 to 2000 A and a crosslinked polymer selected from the group consisting of polystyrene, sulfonated polystyrene, polymethyl methacrylate and polyacrylonitrile coating the surface of the fine holes of the porous silica gel particles in an amount of 5 to 50 wt.% of the polymer to silica gel particles, wherein said crosslinked polymer does not contain any extractable polymer.