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Bare Silica (bare + silica)
Selected AbstractsMicropatterning: Quartz Binding Peptides as Molecular Linkers towards Fabricating Multifunctional Micropatterned Substrates (Adv. Mater.ADVANCED MATERIALS, Issue 3 20093/2009) The cover shows a fluorescent microscopy image of co-assembly of streptavidin functionalized quantum dots (SA-QD) and fluorescein molecules self-assembled using biotinylated and conjugated quartz binding peptides (QBP-bio and QBP-fluorescein). Mehmet Sarikaya and co-workers describe how inorganic binding peptides can act as universal linkers on p. 295. Stamping of the QBP-bio using micro-contact printing is followed by directed assembly of SA-QD (red). The QBP-fluorescein is then immobilized on the bare silica (green) to generate uniform bifunctional micropatterns. [source] Hydrophilic interaction LC of peptides: Columns comparison and clusteringJOURNAL OF SEPARATION SCIENCE, JSS, Issue 6-7 2010Sylvia Van Dorpe Abstract A wide variety of hydrophilic interaction chromatography (HILIC) stationary phase surface chemistries are currently available. Although their selectivity can be considerably different, column comparison or clustering using peptides is limited. In this study, ten pharmaceutically relevant model peptides are analyzed on seven different HILIC columns (bare silica, amide, poly-hydroxyethyl aspartamide, diol and zwitterionic) for the evaluation of their performance and classification. The responses examined include single and multiple responses: plate number, asymmetry factor, LOD, geometric mean resolution, resolution product, time corrected resolution product, peak capacity and chromatographic response function. Column classification was performed using hierarchical clustering and principal component analysis. Moreover, the overall performance quality of the HILIC columns was compared using a linear desirability function. Hierarchical clustering and principal component analysis showed consistent clusters. The zwitterionic phase was clustered apart from the other HILIC columns and both poly-aspartamide columns were clustered together. In addition, the two bare silica phases represent two different clusters, and thus different selectivities. Overall, the responses showed the best performance for one of the bare silica columns (Alltima-Alltech), followed by the zwitterionic phase (ZIC)-HILIC. Thus, these columns, belonging to different clusters, were found to be the best performing systems in pharmaceutical peptide analysis for the selected peptide set. [source] Evaluation of HPLC columns: A study on surface homogeneity of chemically bonded stationary phasesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 3-4 2003Bogus, aw Buszewski Abstract The aim of the current work is to study the heterogeneity of the adsorbent surface on the basis of physicochemical investigations and chromatographic tests. A series of packing materials with octadecyl chains chemically bonded to a silica matrix were prepared for this purpose. The surface and structural properties of bare silica and silica-based octadecyl phases were characterized by porosimetry, elemental analysis, 29Si CP/MAS NMR, etc. The most advanced characterization methods based on adsorption microcalorimetry (heat of wetting) measurements were employed to obtain information about the heterogeneity and topography of unmodified and modified silica gel. For the chromatographic study, these phases were evaluated on the basis of the retention data under non-aqueous conditions. A test series of solutes with various chemical properties, such as pK a values, was used. It was found that heterogeneity of the packing surface results in low HPLC resolution. Use of a non-aqueous mobile phase (n -hexane) reduces analytical interference by eliminating hydrophobic interactions between alkyl ligands and the analyte. [source] Autonomous Movement of Silica and Glass Micro-Objects Based on a Catalytic Molecular Propulsion SystemCHEMISTRY - A EUROPEAN JOURNAL, Issue 10 2008Christoph Stock Dr. Abstract A general approach for the easy functionalization of bare silica and glass surfaces with a synthetic manganese catalyst is reported. Decomposition of H2O2 by this dinuclear metallic center into H2O and O2 induced autonomous movement of silica microparticles and glass micro-sized fibers. Although several mechanisms have been proposed to rationalise movement of particles driven by H2O2 decomposition to O2 and water (recoil from O2 bubbles,36,,45 interfacial tension gradient37,42), it is apparent in the present system that ballistic movement is due to the growth of O2 bubbles. [source] | ||||||||||