Inverse Size-Exclusion Chromatography

Abstract

The most preferred method to separate sample molecules based on their size relative to the pore size is size exclusion chromatography (SEC) (also referred to as gelpermeation, gel-filtration, molecular sieve, or simply gel chromatography) because using a strong solvent, there will be no interaction between the solute molecules and the stationary phase. The inverse version of SEC, inverse size-exclusion chromatography (ISEC) was also described in the middle of the 1970s [1,2], where the pore sizes were determined in the knowledge of the molecule size. Some sources attributed the first description of the ISEC technology incorrectly to Ogston [3] or to Aggerbrandt [4]. There is a plethora of information on the theoretical and experimental aspects of SEC and ISEC and also a number of great reviews have been published. The porous structure of the chromatographic particles is of great complexity and that has a number of consequences during the separation process. The physicochemical properties of high-performance liquid chromatography (HPLC) stationary phases play an important role on column performance and efficiency. The proper characterization of the pore structure and the pore size distribution (PSD) is relevant, because the mass transfer across the particles is greatly affected by the nature of the pores. SEC allows getting a more accurate picture of the impact of the distributions (pore size distribution and polydispersity) on the separation efficiency from ISEC measurements using a proper model. In this chapter, we summarize the most important theories and the newest applications regarding ISEC.