title: Preparation of low flow-resistant methacrylate-based monolithic stationary phases of different hydrophobicity and the application to rapid reversed-phase liquid chromatographic separation of alkylbenzenes at high flow rate and elevated temperature.
abstract: Low flow-resistant alkyl methacrylate-based monolithic stationary phases of different hydrophobicity were constructed for reversed-phase capillary liquid chromatography by thermally initiated radical polymerization of respective methacrylate ester monomer with different alkyl chain (C2, C4, C6, C12, C18) and ethylene glycol dimethacrylate (EDMA) in a 250 microm i.d. fused silica capillary. The hydrophobicity was basically controlled by changing the length and/or the density of the alkyl-chain, while the composition and the ratio of porogenic solvent were adjusted to obtain highly permeable rigid monoliths with adequate column efficiency. Among the prepared monolithic stationary phases, C18-methacrylate monoliths polymerized from a binary porogenic solvent of isoamyl alcohol and 1,4-buthandiol exhibited the most promising performance in terms of hydraulic resistance and column efficiency. The pressure drops of 20-cm long monolithic columns were below approximately 0.4 MPa at a normal linear velocity of 1mm/s (a flow rate of 3 microL/min), and the numbers of theoretical plates for alkylbenzenes mostly exceeded 3000 plates/20 cm. The produced monolithic columns had good mechanical strength for high pressure and temperature, and could be properly operated even at a temperature of 80 degrees C and at a pressure of at least 33 MPa. At 80 degrees C, the theoretical plate numbers reached 6000 plates/20 cm because of the enhanced mass transfer. Due to the novel hydraulic resistance and mechanical strength, the separation time could be reduced 120-fold simply by raising the flow rate and column temperature.
authors.affiliation: Department of Chemistry, Faculty of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Ueki
authors.forename: Tomonari
authors.initials: T
authors.lastname: Umemura
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Iwashita
authors.forename: Tamao
authors.initials: T
authors.lastname: Odake
authors.forename: Hiroki
authors.initials: H
authors.lastname: Haraguchi
authors.forename: Kin-ichi
authors.initials: K
authors.lastname: Tsunoda
mesh_terms: D001554:Benzene / Q000302:isolation & purification*; D002853:Chromatography, Liquid / Q000295:instrumentation*; D006358:Hot Temperature; D008689:Methacrylates / Q000737:chemistry*
chemical_list: D008689:Methacrylates; D001554:Benzene