Adsorption and enthalpic partition retention mechanisms in liquid chromatography of non-charged synthetic polymers

Adsorption and enthalpic partition processes in high performance liquid chromatography (HPLC) of macromolecules are qualitatively described and compared. These two similar but not identical HPLC retention mechanisms result from enthalpic interactions between polymer sample and column packing, which are in different ways affected by interactions between eluent and column packing, and between eluent and sample. The understanding of basic principles of adsorption and enthalpic partition retention mechanisms in polymer HPLC may facilitate the suppression of their unwanted effects, as well as their appropriate coupling with the exclusion retention mechanism. The goal is an easy selection of suitable column packing, mobile phase, and temperature of system to attain desired separation and molecular characterization of particular complex polymer sample. The tailored coupling of enthalpic and entropic retention mechanisms with exclusion allows to either reduce or enhance separation selectivity of polymer species according to their molar masses. In the former case, macromolecules can be separated (practically) irrespectively of their molar mass in terms of other molecular characteristics, namely their chemical structure or physical architecture. On the contrary, increased selectivity of separation in terms of sample molar mass enables improving both the accuracy and speed of analysis. "Flower-like" enthalpic interactions of macromolecules in narrow pores may substantially affect the sample retention.