Incorporation of Single-Wall Carbon Nanotubes into an Organic Polymer Monolithic Stationary Phase for μ-HPLC and Capillary Electrochromatography

Abstract

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.

Polyhedral oligomeric silsesquioxanes as functional monomer to prepare hybrid monolithic columns for capillary electrochromatography and capillary liquid chromatography

“…Nanoparticles were recently explored to functionalize the monoliths with specific selectivity. The approaches are divided into two categories: (i) direct encapsulation of nanoparticles into the monolith in the process of polymerization [21][22][23] and (ii) modification of surface with nanoparticles after monolith formation [24][25][26][27][28][29][30]. The latter approach results in a remarkable increase in the effective surface area of monolith, which was successfully applied for CEC and cLC separation, and solid-phase extraction as well.…”

Applications of nanomaterials in liquid chromatography: Opportunities for separation with high efficiency and selectivity

“…To take advantage of monolithic column architecture and the specific features of SWCNT, Li et al [22] incorporated SWCNT into an organic polymer monolithic stationary phase for micro-HPLC. Pretreated SWCNT dispersed in 2-propanol was used as one of the porogens in the preparation of the monolithic column by employing vinylbenzyl chloride (VBC) as monomer and ethylene glycol dimethacrylate (EDMA) as cross-linker.…”

“…Thus, MS, fluorescence detection, and partial filling techniques are generally used to overcome these adverse effects [17,18]. Use of carbon allotropes, such as fullerene and carbon nanotubes, as separation media in MEKC [19,20], open tubular CEC [21], and monolithic CEC [22] with excellent performance has recently been reported.…”

Photopatterning of tough single‐walled carbon nanotube composites in microfluidic channels and their application in gel‐free separations

“…Gel electrophoresis has found wide application in biomolecule separations and this technique has been used for separation of biomolecules in capillary or microchip mode with interesting results [13][14][15][16][17][18]. The presence of a gel in the buffer, however, often causes problems that include high viscosity and channel blocking.…”

“…Another approach uses organic nanospheres prepared by micellization and polymerization. These nanospheres, with a reportedly low viscosity, were used for the separation of a wide range of DNA sizes [18]. In our approach, the soft gel was immobilized in the microchannel and various gel-free buffers could be used for protein enrichment and separation.…”