Gel permeation chromatography on unmodified silica using aqueous solvents

Summary Chemically unmodified, totally porous, spherical silica particles ( e.g. , LiChrospher from Merck, Darmstadt, G.F.R.) were found to be very suitable for the rapid gel permeation (size-exclusion) chromatography of water-soluble polymers. These materials permit the easy preparation of high efficiency columns. With 10-μm LiChrospher particles, plate numbers > 30,000 per metre were obtained for glucose as a totally permeating solute and water as the mobile phase on 30 × 0.46 cm columns at a flow-rate of 0.5 ml/min. The apparent molecular weight of polyelectrolytes depends on the concentration of the polyelectrolyte and the ionic strength of the mobile phase because of polyelectrolyte expansion and ion-exclusion effects. Adsorption on the silica surface of non-ionic and cationic polymers can be prevented by using a tetramethylammonium salt as a physical modifier.