Capillary zone electrophoretic analysis of positively charged poly(ethylene oxide) macromolecules using non-covalent polycation-coated fused-silica capillary and indirect UV detection

Abstract

Capillary zone electrophoresis was used to show the coupling between NH 2-terminated poly(ethylene oxide) and oligomers of lactic acid activated by transforming carboxyl chain ends to acyl chloride ones. The demonstration was based on the use of fused-silica capillary physically modified by pre-adsorption of polycations in the reversed polarity mode. As poly(ethylene oxide) macromolecules are UV transparent, indirect UV detection was used. A creatinine solution at pH 4.8 was selected as background electrolyte. Commercially available polycations with different structures were tested. It was shown that the reversed electroosmosis could be modulated according to the structure of the polycation. The method was then applied to analyse a commercial α,ω-diamino poly(ethylene oxide), namely Jeffamine ED 600 characterised by a broad mass dispersion. Data showed that the method can detect and separate amino poly(ethylene oxide) of different structures. When applied to analyse post coupling products, no free NH 2-terminated poly(ethylene oxide) segments were detected. Moreover, the method allowed detection of water-soluble oligomers generated by partial degradation of lactic segments during the reaction.