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

Liquid chromatography of macromolecules at the point of exclusion-adsorptio n transition (LC FEAT) is based on a controlled balance between entropic (e xclusion) and enthalpic (adsorption) effects within LC system that results in the loss of separation according to the molar mass. Consequently, polyme r species exhibiting the same adsorptivity but different sizes are eluted i n one single retention volume that roughly corresponds to the total volume of liquid within column. At the same time, other kinds of polymer chains wi th different adsorptivities are eluted according to either exclusion or ads orption mechanism. This may allow discrimination and independent characteri zation of chemically different species such as functionalized macromolecule s, block- and graft- copolymers and polymer blends. Differences in the phys ical structure of macromolecules, for example in their stereoregularity rep resent an alternative separation parameter. Four approaches to the exclusion-adsorption transition in liquid chromatogr aphy 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 limi ting conditions of adsorption (LC LCA) and liquid chromatography under limi ting 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 d iscussed in the present review.