title: New generation of sterically protected C18 stationary phases containing embedded urea groups for use in high-performance liquid chromatography.
abstract: New monofunctional C18 urea stationary phases with sterically protecting dimethyl and diisopropyl groups were prepared by a single step modification process. ProntoSil spherical silica (3 microm) was chemically modified with the monofunctional ethoxysilanes, [(3-octadecylurea)propyl]dimethyl and [(3-octadecylurea)propyl]diisopropyl ethoxysilanes. The phases were characterized by elemental analysis, infrared and solid-state 29Si and 13C NMR spectroscopies. Chromatographic characterizations of the new phases in 50x3.9 mm HPLC columns were performed by the separation of two different test mixtures, containing nonpolar, polar and highly basic compounds.
authors.affiliation: Instituto de Química, Universidade Estadual de Campinas, Caixa Postal 6154, 13083-970 Campinas, São Paulo, Brazil.
authors.forename: César Ricardo
authors.initials: CR
authors.lastname: Silva
authors.forename: Isabel Cristina Sales Fontes
authors.initials: IC
authors.lastname: Jardim
authors.forename: Claudio
authors.initials: C
authors.lastname: Airoldi
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation*; D009682:Magnetic Resonance Spectroscopy; D013055:Spectrophotometry, Infrared; D014508:Urea / Q000737:chemistry*
chemical_list: D014508:Urea