title: Development of new urea-functionalized silica stationary phases. Characterization and chromatographic performance.
abstract: New urea-functionalized silica stationary phases were prepared by a single-step surface modification through reaction of LiChrosorb Si100 (5 microm particle size) with a homologous series of alkoxysilanes, synthesized in our laboratory, with the general formula (CH3CH2O)3Si(CH2)3NHC(O)NH(CH2)nCH3, where n=4, 6 and 11. The modified silicas were characterized by elemental analysis of carbon and nitrogen, solid-state 29Si- and 13C-cross polarization magic angle spinning nuclear magnetic resonance and nitrogen adsorption isotherms at 77 K. Chromatographic evaluation of the three urea-functionalized silicas in 150x3.9 mm I.D. HPLC columns was carried out by the separation of a test mixture composed of uracil, acetophenone, benzene, toluene and naphthalene, using acetonitrile-water as mobile phase. These new stationary phases, with embedded polar urea groups, are very promising when compared with amide phases prepared by the conventional two-step modification process. A single-step reaction process silica modification is better for obtaining a well-characterized and homogeneous modified surface.
authors.affiliation: Instituto de Química, Universidade Estadual de Campinas, São Paulo, Brazil.
authors.forename: C R
authors.initials: CR
authors.lastname: Silva
authors.forename: I C
authors.initials: IC
authors.lastname: Jardim
authors.forename: C
authors.initials: C
authors.lastname: Airoldi
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation*; D009682:Magnetic Resonance Spectroscopy; D012822:Silicon Dioxide / Q000737:chemistry*; D014508:Urea / Q000737:chemistry*
chemical_list: D012822:Silicon Dioxide; D014508:Urea