Macroporous, monodisperse particles and their application in aqueous size exclusion chromatography of high molecular weight polysaccharides

Three different types of 15 mu m macroporous polymer particles (MP) based on poly(styrene-co-divinylbenzene), all with an extreme degree of monodispersity, were prepared by the method of 'activated swelling'. The type and relative content of low molecular weight compounds used as pore-forming agents (porogens) ensured that the total pore volume was confined to large pores with radii larger than 300 Angstrom, and with an increasingly larger fraction of the pore volume shifted towards very large pores (> 2000 Angstrom). A hydrophilic layer was covalently linked to the particles to eliminate their hydrophobic character, and they were subsequently tested in aqueous size exclusion chromatography (SEC). Favourable chromatographic properties generally associated with monosized particles were obtained, and column packing as well as the separations were performed with very low back pressures. The particles were found to be suitable for SEC of a series of high molecular weight polysaccharides, irrespective of their charge (anionic, cationic and neutral). The shift in pore size distribution towards very large pores resulted in a corresponding shift in the range of molecular weights (strictly, hydrodynamic volumes) where separation took place. For particles with 70% of the pore volume confined to pores with radii larger than 2000 Angstrom, it was estimated that the molecular weight range of polysaccharides of the pullulan type accessible to SEC was extended up to ca. 10(8). The corresponding value for an extended, rod-like, triple-helical polysaccharide (scleroglucan) was 10(7). Copyright (C) 1996 Elsevier Science Limited.