Gradient HPLC of Copolymers and Chromatographic Cross-Fractionation

&quote;The problems involved in separating complex macromolecules require under- standing not only the chromatographic process but also the physicochemical behavior of the solutes.&quote; This sentence from the pen of Phyllis R. Brown 1, University of Rhode Island, can certainly be applied to synthetic copolymers whose structure is very complex indeed. Thus it may be forgiven that a book on copolymer HPLC has been written not by a trained chromatographer but by someone from the polymer side. The HPLC of synthetic polymers is often understood to mean only a synonym for size exclusion chromatography. The latter method separates polymers according to the size of the macromolecules and enables the molecular weight distribution of a sample to be evaluated. But as early as 1936, Mark and Saito attempted chromatographic fractionation of cellulose acetate on a charcoal-like adsorbent made from blood. HPLC adsorption chromatography was first applied to copolymer analysis by Teramachi et al. in 1979. Since then, another branch of polymer HPLC has arisen which has the capacity of separating copolymers by composition and enables the chemical composition distribution to be evaluated. The technique requires a suitable elution program and is mainly carried out as gradient elution.