fraction which is deposited onto the support solubility is near a minimum when the ph of the solvent mixture is equal to that obtained when the initial ph of the buffered water is near the iep of the protein as is well known see for example r scopes protein purification springer verlag n y 1986 pp 52 60 under the above constraints protein will not precipitate as separate particles which would be difficult to remove from the support particles in any event as a first actual treatment step in the present method either an untreated porous silica support or a prior treated porous silica support is contacted with an aqueous solution into which a protein has been dissolved as mentioned the protein is selected relative to the pore diameter of the porous silica so as to be size excluded from the internal surfaces of the porous silica thus it preferably has a molecular size of 40 to 400 u00e5 it should also be water soluble the preferred proteins are serum albumin bovine serum albumin bsa egg conalbumin ovalbumin and serum u03b1 glycoprotein the amount of protein coating needed to saturate a protein adsorptive support depends on the particle diameter of the support and is independent of pore diameter if the protein is.