Calibration of Retention Volume in Size Exclusion Chromatography by Hydrodynamic Radius

Abstract

Universal calibration of retention volume in size exclusion chromatography (SEC) is examined using Gaussian chain models for linear and branched chain polymers. The question is which molecular dimension, the radius of gyration Rg or the hydrodynamic radius RH, determines the partitioning of polymers of different architectures. The partition coefficient K is calculated for asymmetric star polymers, two-branch-point polymers, and comb polymers with a pore of slit geometry of opening d. The plots of K as a function of RH/d for these polymers nearly overlap with each other, whereas the agreement is poorer for the plots of K as a function of Rg/d. The experimental data of the SEC retention volume recently obtained by Sun et al. for linear and branched polyethylene [Macromolecules 2004, 37, 4304] are used to demonstrate that the quality of the calibration curve using RH is superior to the one using Rg and comparable to the one using hydrodynamic volume widely practiced in the community. The universal calibration by RH will facilitate inferring the branching structure of a given chain polymer from its SEC retention volume, since calculation of RH is much easier for any chain architecture compared with the hydrodynamic volume.