Size Exclusion Chromatography:

In this case, column packings are either semi-rigid, cross-linked macromolecular polymers or rigid and controlled pore size glasses or silicas. The semi-rigid materials swell and care must be taken to their use limited to a maximum pressure of 300 psi due to bed compressibility. The styrene-divinyl benzene polymers allow fractionation within a molecular weight range of 100 to 5000 million. Partially sulphonated polystyrene beads are compatible with aqueous systems and non-sulphonated ones with non-aqueous systems with bead diameters ~5 µm.

Another class of hydrophilic porous packing is prepared by suspension polymerization of 2-hydroxyethyl methacrylate with ethylene dimethacrylate. These packings can withstand pressures up to 3000 psi and are usable with aqueous systems and with a variety of polar organic solvents. Porous glasses and silicas cover a wide range of pore size diameters. For example, a series of particle size diameters and operating ranges of molecular weights are listed in Table 8.3.

Table: Correlation of Pore Size Diameter and Operating Range of Mol. Wt

These packings are chemically resistant at pH <10 and can be used with aqueous and polar organic solvents. With nonpolar solvents, it is desirable to deactivate the surface by silylation. Porous inorganic packings have distinct advantages over organic exclusion packings. The surface of a typical hydrophilic packing has the following structure;

Columns can be used routinely and indefinitely after calibration, without any possibility of sample contamination or biodegradation.