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Individual Columns (individual + column)
Selected AbstractsA spiro-linked pyrene,naphthoquinoneACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2000Joseph A. Potenza The title molecule, 2,-pyrenylspiro[2,3-dihydro-1H -cyclopenta[b]naphthalene-2,5,-1,,3,-dioxane]-4,9-dione, C32H22O4, contains an electron-donating pyrene group spiro-linked to an electron-accepting naphthoquinone. The molecules are V-shaped in profile and stack to form columns along b with alternating, approximately coplanar, pyrene and naphthoquinone fragments. Intermolecular contacts within a column are consistent with some degree of , contact and possible long-range delocalization. Individual columns form a herringbone pattern when the crystal is viewed along b. [source] Visible light initiated polymerization of styrenic monolithic stationary phases using 470,nm light emitting diode arraysJOURNAL OF SEPARATION SCIENCE, JSS, Issue 1 2010Zarah Walsh Abstract Poly(styrene- co -divinylbenzene) monolithic stationary phases have been synthesized for the first time by photoinitiated polymerization. An initiator composed of (+)-(S)-camphorquinone/ethyl-4-dimethylaminobenzoate/N- methoxy-4-phenylpyridinium tetrafluoroborate was activated using a 470,nm light emitting diode array as the light source. Spatially controlled polymerization of styrenic monoliths has been achieved within specific sections of a 100,,m id polytetrafluoroethylene-coated fused-silica capillary using simple photo masking. The sharpness of the edges was confirmed by optical microscopy, while SEM was used to verify a typical porous, globular morphology. Flow resistance data were used to assess the permeability of the monoliths and they were found to have good flow through properties with a flow resistance of 0.725,MPa/cm at 1,,L/min (water, 20°C). Conductivity profiling along the length of the capillary was used to assess their lateral homogeneity. Monoliths which were axially rotated during polymerization were found to be homogeneous along the whole length of the capillary. The monolithic stationary phases were applied to the RP gradient separation of a mixture of proteins. Column fabrication showed excellent reproducibility with the retention factor (k) having a RSD value of 2.6% for the batch and less than 1.73% on individual columns. [source] Optimisation of gradient HPLC analysis of phenolic compounds and flavonoids in beer using a CoulArray detectorJOURNAL OF SEPARATION SCIENCE, JSS, Issue 15-16 2004Lucie, ehová Abstract A method was developed for simultaneous analysis of natural antioxidants in beer using multichannel electrochemical detection with a CoulArray detector, which enables selective and sensitive antioxidant detection in gradient HPLC and facilitates the identification of analytes based on the ratios of signals recorded at different potentials applied to the detection cells arranged in series. The separation conditions were optimised for 27 phenolic compounds including derivatives of benzoic and cinnamic acids, flavones, and a few related glycosides identified in beer samples. Separation selectivities of 11 columns with different stationary phase chemistries were compared, and the pH and gradient programs were optimised for the individual columns to provide best resolution and high number of resolved peaks, using the window-diagram approach. The effects of pH on the sensitivity of electrochemical coulometric detection were considered in the optimisation approach. The optimised conditions were applied to the analysis of real beer samples. [source] Solving multicomponent chiral separation challenges using a new SFC tandem column screening toolCHIRALITY, Issue 3 2007Christopher J. Welch Abstract A tool for improved tandem column chiral supercritical fluid chromatography (SFC) method development screening was prepared by modification of a commercial analytical SFC instrument with two different software-controllable, six position high-pressure column selection valves, each controlling a bank of five different columns and a pass through line. The resulting instrument, which has the ability to screen 10 different individual columns and 25 different tandem column arrangements, is a useful tool for facilitating the screening of tandem column SFC arrangements for separation of complex mixtures of stereoisomers or other multicomponent mixtures. Strategies for optimal use of the instrument are discussed, and several examples of the use of the instrument in developing tandem SFC methods for resolution of multicomponent mixtures are presented. Chirality, 2007. © 2006 Wiley-Liss, Inc. [source] | ||||||||||