Macroporous particles:
These are recently introduced graphitized carbon and styrene-divinylbenzene polymers having large channels besides micropores. The rigid, porous polymeric macroporous beads do not swell or shrink with changes in the ionic strength of the mobile phase (can be used over an extended pH range of 1 and 13) or deform at high velocities and are most suited for separations in nonaqeous media. Those materials have raised the choice of stationary phases and the scope of HPLC that particularly for highly polar and basic substances.
An illustration of various types of bonded phases used in HPLC is shown in Figure where different topographies are obtained depending on the nature of the ligand. It may be noted that different packing materials are used in different type of techniques of adsorption, ion-exchange, partition, size exclusion chromatography.
Figure: Various shapes of bonded HPLC column packing materials (a) Types of bonded phases, (b) Topography of ligands and (c) Size of ligands