Incorporation of carbon nanotubes in porous polymer monolithic capillary columns to enhance the chromatographic separation of small molecules

Abstract

Multiwalled carbon nanotubes have been entrapped in monolithic poly(glycidyl methacrylate-co-ethylene dimethacrylate) capillary columns to afford stationary phases with enhanced liquid chromatographic performance for small molecules in the reversed phase. While the column with no nanotubes exhibited an efficiency of only 1800 plates/m, addition of a small amount of nanotubes to the polymerization mixture increased the efficiency to over 15,000 and 35,000 plates/m at flow rates of 1 and 0.15 μL/min, respectively. Alternatively, the native glycidyl methacrylate-based monolith was functionalized with ammonia and, then, shortened carbon nanotubes, bearing carboxyl functionalities, were attached to the pore surface through the aid of electrostatic interactions with the amine functionalities. Reducing the pore size of the monolith enhanced the column efficiency for the retained analyte, benzene, to 30,000 plates/m at a flow rate of 0.25 μL/min. Addition of tetrahydrofuran to the typical aqueous acetonitrile eluents improved the peak shape and increased the column efficiency to 44,000 plates/m calculated for the retained benzene peak.

Nano-Doped Monolithic Materials for Molecular Separation

“…The success of MWCNT-doped monoliths in protein retention was due to the hydrophobic nature and π-π interactions they establish with proteinaceous targets and aromatic amino acid residues [82]. Similarly, an enhancement in separation performance was obtained in the separation of uracil and alkylbenzenes using poly(GMA-co-EDMA-MWCNT) monoliths and poly(GMA-co-EDMA) monoliths modified with MWCNT [83]. The resultant number of plates observed were as follows: (i) blank poly(GMA-co-EDMA), 1,800 plates/m; (ii) poly(GMA-co-EDMA-MWCNT), 15,000 and 35,000 plates/m for flow rates of 1 and 0.15 µL/min, respectively; and (iii) surface modified poly(GMA-co-EDMA) using MWCNT, 23,000 plates/m at 0.25 µL/min.…”

Advances in monolithic silica columns for high-performance liquid chromatography

“…Chambers et al made a monolithic poly(glycidyl methacrylate-co-ethylene dimethacrylate) capillary columns by incorporating multiwalled carbon nanotubules for the better performance of the separation. They observed an 1800 plates/m (without nanotubes) and 15,000 and a 35,000 plates/m at a flow rate of 1 and 0.15 μL/ min, respectively (Chambers, Svec, and Fréchet, 2011). Urban et al prepared hypercrosslinked porous polymer monolithic capillary columns by using poly (styrene-co-vinylbenzyl chloride-co-divinylbenzene) precursor monolith that was swollen in 1,2-dichloroethane and hypercrosslinked via Friedel-Crafts reaction catalyzed by ferric chloride.…”

Application of Carbon Nanotubes in Chiral and Achiral Separations of Pharmaceuticals, Biologics and Chemicals

“…Based on chirality, the synthesis of CNTs to CNTs or other interfering materials. For example, incorporation of CNTs in polymeric stationary phase revealed that polymer played the major role of chromatographic separation which masked the real role of separation by CNTs [26,27]. CNTs have been also shown to play the major role of chromatographic separation due to LUMO energy [28].…”