Liquid chromatography of macromolecules at the point of exclusion-adsorption transition

Liquid chromatography of macromolecules at the point of exclusion-adsorption transition (LC FEAT) is based on a controlled balance between entropic (exclusion) and enthalpic (adsorption) effects within LC system that results in the loss of separation according to the molar mass. Consequently, polymer species exhibiting the same adsorptivity but different sizes are eluted in one single retention volume that roughly corresponds to the total volume of liquid within column. At the same time, other kinds of polymer chains with different adsorptivities are eluted according to either exclusion or adsorption mechanism. This may allow discrimination and independent characterization of chemically different species such as functionalized macromolecules, block- and graft- copolymers and polymer blends. Differences in the physical structure of macromolecules, for example in their stereoregularity represent an alternative separation parameter. Four approaches to the exclusion-adsorption transition in liquid chromatography of macromolecules were so far proposed, viz. liquid chromatography at the critical adsorption point (LC CAP), liquid chromatography at the theta exclusion-adsorption conditions (LC TEA), liquid chromatography- under limiting conditions of adsorption (LC LCA) and liquid chromatography under limiting conditions of desorption (LC LCD). The principles of LC CAP, LC TEA, LC LCA and LC LCD and their applicability are elucidated and the advantages and problems of particular methods are discussed in the present review.