The molecular weight separation and column dispersion for a number of SEC columns packed with various packing materials were calibrated simultaneously using narrow MWD polystyrene standards as probe. In all the case the spreading factor increases with increasing molecular weight of the probe

but its magnitude is closely related to the surface structure in the pore of the packings. As the porous silica beads with larger pore diameter possess a small specific surface area and a more smooth pore surface structure

the movement of the solute mole-cule is less restricted

the spreading factor of the high molecular weight polystyrene (M-106) is only two to three times as many as that ofthe low molecular weight one. For the crosslinked polystyrene gel the specific surface area is laregr and its pore surface structure is rougher than that of silica beads

the spreading factor of high moldcular weight probe increases inseveral ten-folds. It indicates that the movement of the solute molecule is more hindered

which could be explained by the fact that there are some shorter or longer free chain ends on the surface of the skeleton forming the permanent pore of the crosslinked organic gels.