The relationship between the content of hydroxyl groups on the surface of porous silica gels used as packings for GPC and the adsorption effects was investigated. Toluene was used as eluent and hydroxyl-end blocked polydimethylsiloxane as polymer sample. By modifying the porous silica gels with hexamethyldisilazane or by adding a small amount of a suppressant to the solvent carrier to reduced the adsorpting of polymers onto the surface of gels

was found to be unsatisfactory. An effective method for suppressing the adsorption by blocking the hydroxyl groups on the ends of polymer chains with trimethylchlorosilane has been proposed.