title: Silica-based monolithic columns with mixed-mode reversed-phase/weak anion-exchange selectivity principle for high-performance liquid chromatography.
abstract: This article describes the synthesis, chromatographic characterization, and performance evaluation of analytical (100 x 4.6 mm id) and semipreparative (100 x 10 mm id) monolithic silica columns with mixed-mode RP/weak anion-exchange (RP/WAX) surface modification. The monolithic RP/WAX columns were obtained by immobilization of N-(10-undecenoyl)-3-aminoquinuclidine onto thiol-modified monolithic silica columns (Chromolith) by a radical addition reaction. Their chromatographic characterization by Engelhardt and Tanaka tests revealed slightly lower hydrophobic selectivities than C-8 phases, as well as higher polarity and also improved shape selectivity than RP-18e silica rods. The surface modification enabled separation by both RP and anion-exchange chromatography principles, and thus showed complementary selectivities to the RP-18e monoliths. The mixed-mode monoliths have been tested for the separation of peptides and turned out to be particularly useful for hydrophilic acidic peptides, which are usually insufficiently retained on RP-18e monolithic columns. Compared to a corresponding particulate RP/WAX column (5 microm, 10 nm pore diameter), the analytical RP/WAX monolith caused lower system pressure drops and showed, as expected, higher efficiency (e.g. by a factor of about 2.5 lower C-term for a tetrapeptide). The upscaling from the analytical to semipreparative column dimension was also successful.
authors.affiliation: Christian Doppler Laboratory for Molecular Recognition Materials, Department of Analytical and Food Chemistry, University of Vienna, Vienna, Austria.
authors.forename: Raquel
authors.initials: R
authors.lastname: Nogueira
authors.forename: Dieter
authors.initials: D
authors.lastname: Lubda
authors.forename: Alexander
authors.initials: A
authors.lastname: Leitner
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Bicker
authors.forename: Norbert M
authors.initials: NM
authors.lastname: Maier
authors.forename: Michael
authors.initials: M
authors.lastname: Lämmerhofer
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Lindner
mesh_terms: D000838:Anions / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation* / Q000379:methods; D002852:Chromatography, Ion Exchange / Q000295:instrumentation* / Q000379:methods; D057927:Hydrophobic and Hydrophilic Interactions; D008422:Materials Testing; D015394:Molecular Structure; D010316:Particle Size; D016062:Porosity; D012822:Silicon Dioxide / Q000737:chemistry*
chemical_list: D000838:Anions; D012822:Silicon Dioxide