title: Calix[4] open-chain crown ether-modified, vinyl-functionalized hybrid silica monolith for capillary electrochromatography.
abstract: A novel calix[4] open-chain crown ether (p-tert-butylcalix[4]arene-1,3-bis(allyloxyethy) ether)-modified, organic-inorganic hybrid silica-based monolithic column possessing vinyl ligands for CEC is described. The monolithic silica matrix containing a vinyl functionality was synthesized by in situ cocondensation of tetramethoxysilane (TMOS) and vinyltrimethoxysilane (VTMS) via sol-gel process and chemically modified with calix[4] open-chain crown ether by free radical polymerization procedure using alpha, alpha'-azobisisobutyronitrile (AIBN) as an initiator. Morphology of the monolithic column was examined by SEM and the successful incorporation of calix[4] open-chain crown ether to the vinyl-hybrid monolith was characterized by infrared (IR) spectra. Compared with an unmodified vinyl-hybrid monolithic column, slightly stronger EOF at pH >7.5 was observed for this monolithic column due to the ionization of phenolic hydroxyls on the lower rim of calix[4]arene. VTMS/TMOS ratios in the reaction mixture were varied and 1:4 was found to be optimum to obtain homogeneous monolith with good permeability. The performance of the column was evaluated by nucleotides, beta-blockers, neurotransmitters, and PAHs as test solutes and compared with that of unmodified vinyl-hybrid monolithic column. Greatly improved column performance was obtained due to the host-guest interaction and intermolecular hydrogen bonding provided by the calix[4] open-chain crown ether moiety. The column efficiencies for neurotransmitters and nucleotides are up to 120 000 and 110 000 plates/m, respectively. Migration time and theoretical plate number reproducibilities were reasonable with RSDs less than 1.0 and 1.8% each for within column runs and not more than 7.2 and 8.6% each for column-to-column measurements, using four nucleotides as test solutes.
authors.affiliation: Department of Chemistry, Wuhan University, Wuhan, P. R. China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Tian
authors.forename: Lianfeng
authors.initials: L
authors.lastname: Zhang
authors.forename: Zhaorui
authors.initials: Z
authors.lastname: Zeng
authors.forename: Haibing
authors.initials: H
authors.lastname: Li
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000032:analysis; D047250:Calixarenes / Q000737:chemistry; D053801:Capillary Electrochromatography / Q000379:methods*; D043844:Crown Ethers / Q000737:chemistry*; D018377:Neurotransmitter Agents / Q000032:analysis; D009570:Nitriles / Q000737:chemistry; D009711:Nucleotides / Q000032:analysis; D044367:Phase Transition; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis; D012821:Silanes / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry*; D014753:Vinyl Compounds / Q000737:chemistry
chemical_list: C529209:4-tert-butylcalix(4)arene-1,3-bis(allyloxyethyl) ether; D000319:Adrenergic beta-Antagonists; D043844:Crown Ethers; D018377:Neurotransmitter Agents; D009570:Nitriles; D009711:Nucleotides; D011084:Polycyclic Aromatic Hydrocarbons; D012821:Silanes; D014753:Vinyl Compounds; C529208:trimethoxyvinylsilane; D047250:Calixarenes; C061205:tetramethoxysilane; D012822:Silicon Dioxide; C004526:azobis(isobutyronitrile)