Application of Novel Separation Field, Polymer Aggregate, to Capillary Electrophoresis

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Some amphiphilic block-copolymers consisting of poly [(N-acylimino) ethylene] structure, which has hydrophilic blocks and hydrophobic blocks, form aggregates of 100 nm diameter in aqueous media. The polymer aggregate (AG) was added to the running solution of capillary electrophoresis (CE), and the further addition of a small amount of anionic surfactant, such as SDS, to provide negative charges onto the aggregate surface resulted in the functioning of AG as a pseudo-stationary phase (AG-CE). Thus, neutral compounds, such as phenols, were migrated in the order of lipophilicity. Compared to the conventional micellar electrokinetic chromatography by use of SDS (SDS-MEKC), the migration of nitrophenols was greatly retarded. Such anionic species are incorporated neither into AG nor into SDS micelles. The charge density of AG is much smaller than that of SDS micelles. Therefore, it appears that the migration of neutral species, which are incorporated in SDS micelles are smaller than that of the anionic species, whereas such a delay in the neutral species migration was not observed for the species incorporated in AG.Consequently, in AG-CE the migration of anionic species is smaller than that of neutral species incorporated in AG, unlike SDS-MEKC.To attain a novel micellar chromatography, the AG was added to the mobile phase in a reversed-phase chromatography (AG-LC). For the separation of naphthalenesulfonate derivatives, AG-LC showed a considerably different selectivity from that for the conventional micellar chromatography.In the future, the expression of further molecular recognition ability through the molecular modification of amphiphilic block-copolymers will hopefully lead to new applications of AG to CE and related chromatography technologies.