a method of separating organic materials is disclosed utilizing a chromatographic packing material . this packing material includes a coated support material which is a chromatographically suitable substrate . an immobilized butadiene acrylonitrile polymer coating is provided on the substrate . the copolymer can be crosslinked by gamma radiation , or by means of a crosslinking agent such as dicumyl peroxide . the support material can be silica , alumina , diatomaceous earth , zeolite , porous glass or carbon , but preferably is spherical lamellar shaped crystals of aluminum hydroxide . the aluminum hydroxide crystals are bonded together at a central core and extend radially outward from a central core with a particle density ranging from 0 . 3 to 2 . 5 g / cm 3 and a diameter of 2 to 150 microns .