Liquid Chromatography of Macromolecules under Limiting Conditions of Desorption. 1. Principles of the Method

Abstract

The liquid chromatography of macromolecules under limiting conditions of desorption (LC LCD) is based on a combination of exclusion and adsorption separation mechanisms. Eluent promotes desorption of macromolecules that are dissolved in an adsorption-promoting liquid and injected into a liquid chromatographic (LC) column packed with porous adsorptive packing. The zone of sample solvent forms an “adsorption promoting barrier”. Under properly chosen, “limiting”, conditions the transport of adsorbing polymer species along the column is slowed since they cannot pass the above adsorption-promoting barrier. As result, macromolecules of various sizes and molar masses leave LC column in the form of a rather narrow band immediately behind the zone of their initial solvent. At the same time, other kinds of polymer chains which exhibit lower affinity toward column packing and less adsorption surmount the zone of their original solvent. They are eluted in the size exclusion chromatographic mode. In this way macromolecules with different chemical structures can be discriminated. The LC LCD idea has been tested with a model system comprising poly(methyl methacrylate) probes, silica gel column packing, toluene (adsorbing liquid), and tetrahydrofuran (desorbing liquid). Some applications of this novel LC procedure have been proposed. They include separation of two-component and multicomponent blends, various kinds of copolymers, and oligomers.