Size-exclusion chromatography of polyelectrolytes: comparison with theory

A theoretical model for the free energy of partitioning of charged spheres into cylindrical pores of like charge, based on the linearized Poisson-Boltzmann equation, has been evaluated vis-a-vis the elution behavior of anionic polyelectrolytes on size-exclusion chromatography columns packed with porous glass beads. Theoretical predictions of the dependence of the chromatographic partition coefficient on the relative dimensions of solute and pore were compared to experimental results obtained over a wide range of polyion molecular weights, pore sizes, and mobile-phase ionic strengths. Good agreement was found when the polyelectrolyte was modeled as a porous charged sphere, with the dimensions of its equivalent hydrodynamic sphere and a volume charge density dictated by an adjustable effective degree of dissociation.