title: Size exclusion chromatography does not require pores.
abstract: Separation of macromolecules on the basis of their molecular weight by size exclusion chromatography has long been considered to be caused by the geometry-dependent partition of macromolecules between a continuous phase and the porous interior of a gel or cross-linked bead. The volume of a pore accessible to a solute is limited by its relative dimensions, so larger molecules will have access to a smaller volume and will remain in a bead for a shorter time than smaller solutes. Our recent alternate picture proposes that the partition coefficient can be calculated from a thermodynamic model for the free energy of mixing of the solute with the gel phase. Size-dependent exclusion caused by the unfavorable entropy of mixing associated with the partition is predicted; the magnitude of the effect is modified by enthalpic interactions between the solute and the gel phase. This concept is extended here to describe the partition of macromolecules into a layer of terminally attached polymer chains grafted onto a solid bead. Both simple mean field and self-consistent field theory calculations predict size-dependent entropic exclusion. Experimental results obtained with neutral polymer chains grafted onto solid polystyrene latex beads confirm the predictions.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, Canada V6T 2B5. don@pathology.ubc.ca
authors.forename: D E
authors.initials: DE
authors.lastname: Brooks
authors.forename: C A
authors.initials: CA
authors.lastname: Haynes
authors.forename: D
authors.initials: D
authors.lastname: Hritcu
authors.forename: B M
authors.initials: BM
authors.lastname: Steels
authors.forename: W
authors.initials: W
authors.lastname: Müller
mesh_terms: D002845:Chromatography / Q000295:instrumentation* / Q000379:methods*; D008863:Microspheres; D010316:Particle Size; D011108:Polymers
chemical_list: D011108:Polymers