The average pore diameter of the pore in porous packing. The pore diameter is important in that it must allow free diffusion of solute molecules into and out of the pore so that the solute can interact with the stationary phase. In SEC. the packings have different pore diameters, and therefore molecules of different sizes can be separated. For a typical adsorbent such as silica gel. 60-Å and 100-Å pore diameters are most popular. For packings used for the separation of biomolecules, pore diameters > 300 Å are used.