Incorporation of single-wall carbon nanotubes into an organic polymer monolithic stationary phase for mu-HPLC and capillary electrochromatography

Single-wall carbon nanotubes (SWNT) were incorporated into an organic polymer monolith containing vinylbenzyl chloride (VBC) and ethylene dimethacrylate (EDMA) to form a novel monolithic stationary phase for high-performance liquid chromatography (HPLC) and capillary electrochromatography (CEC). The retention behavior of neutral compounds on this poly(VBC-EDMA-SWNT) monolith was examined by separating a mixture of small organic molecules using micro-HPLC. The result indicated that incorporation of SWNT enhanced chromatographic retention of small neutral molecules in reversed-phase HPLC presumably because of their strongly hydrophobic characteristics. The stationary phase was formed inside a fused-silica capillary whose lumen was coated with covalently bound polyethyleneimine (PEI). The annular electroosmotic flow (EOF) generated by the PEI coating allowed peptide separation by CEC in the counterdirectional mode. Comparison of peptide separations on poly(VBC-EDMA-SWNT) and on poly(VBC-EDMA) with annular EOF generation revealed that the incorporation of SWNT into the monolithic stationary phase improved peak efficiency and influenced chromatographic retention. The structures of pretreated SWNT and poly(VBC-EDMA-SWNT) monolith were examined by high-resolution transmission electron microscopy, Raman spectroscopy, scanning electron microscopy, and multipoint BET nitrogen adsorption/desorption.