title: Fabrication and evaluation of an organic monolithic column based upon the polymerisation of hexyl methacrylate with 1,6-hexanediol ethoxylate diacrylate for the separation of small molecules by capillary liquid chromatography.
abstract: This paper describes the fabrication of a new porous monolith, prepared in 100μm i.d. capillaries by the co-polymerisation of hexyl methacrylate with 1,6-hexanediol ethoxylate diacrylate, poly (HMA-co-1,6 HEDA), in the presence of azobisisobutyronitrile, 1, 4-butanediol and 1-propanol were used as porogens for the monoliths; the monoliths were then used as a stationary phase for capillary liquid chromatography. Two cross linkers namely 1,6 HEDA and EDMA were utilised in order to investigate the effects of cross linker length on the separation efficiency of small molecules, and it was found that the efficiency of the separation improved tenfold when using the longer cross linker, 1,6 HEDA. This improvement is associated with the increase in number of methylene groups which resulted in an increased number of mesopores, less than 50nm. The 1,6 HEDA based monolith showed a high porosity (90%) and no evidence of swelling or shrinking with the use of organic solvents. Moreover, the 1,6 HEDA monolith demonstrated high reproducibility for the separation of the retained compounds anisole and naphthalene; these showed retention time RSDs of 1.79% and 2.74% respectively. The fabricated monolith also demonstrated high selectivity for neutral non-polar molecules, weak acids, and basic molecules. The asymmetry factors for basic molecules (nortriptyline and amitriptyline) were 1.5 and 1.3 respectively, indicating slight tailing, which is often noticeable on silica based phases due to secondary interactions between basic moieties and the hydroxyl groups of the silica.
authors.affiliation: Analytical and Environmental Science Division, Faculty of Life Sciences & Medicine, King's College London, London SE1 9NH, United Kingdom.
authors.forename: Wael
authors.initials: W
authors.lastname: Alshitari
authors.affiliation: Pharmaceutical Science Division, Faculty of Life Sciences & Medicine, King's College London, London SE1 9NH, United Kingdom.
authors.forename: Cristina Legido
authors.initials: CL
authors.lastname: Quigley
authors.affiliation: Analytical and Environmental Science Division, Faculty of Life Sciences & Medicine, King's College London, London SE1 9NH, United Kingdom. Electronic address: norman.2.smith@kcl.ac.uk.
authors.forename: Norman
authors.initials: N
authors.lastname: Smith
mesh_terms: D000179:Acrylates / Q000737:chemistry*; D002853:Chromatography, Liquid / Q000295:instrumentation* / Q000379:methods; D008689:Methacrylates / Q000737:chemistry*; D015394:Molecular Structure; D058105:Polymerization; D016062:Porosity; D054852:Small Molecule Libraries / Q000302:isolation & purification*
chemical_list: D000179:Acrylates; D008689:Methacrylates; D054852:Small Molecule Libraries; C533795:hexyl methacrylate; C020355:1,6-hexanediol diacrylate; C090921:1,6-hexanediol dimethacrylate
keywords: 1,6-Hexanediol ethoxylate diacrylate; Capillary liquid chromatography; Hexyl methacrylate; Organic monolith