A Phenomenological Investigation of N-alkyl-bonded Phases in Reversed--phase-liquid Chromatography PDF Download
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Author: Shih Hsien Hsu
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Shih Hsien Hsu
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: Shih Hsien Hsu
Publisher:
ISBN:
Category : Liquid chromatography
Languages : en
Pages : 444
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 726
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Investigation and control of alkylsilane stationary phase structure in reversed phase liquid chromatography is presented. Raman spectroscopy is used to probe thealkyl chain conformational order and interchain coupling as a function of various chromatographic conditions. A new method is further developed to fabricate alkylsilane stationary phases with controlled surface coverage. The alkyl chain conformational order and interchain coupling of a series of high-density docosylsilane (C22) bonded stationary phases is shown as a function of temperature, surface coverage, polymerization method, common solvents and solutes. The conformational order of C22 stationary phases is compared to that of octadecylsilane (C18) stationary phases to understand the chain length effect on stationary phase structure. The conformational order information as indicated by Raman spectral order indicators for a C22 phase are correlated with the capacity factor and separation efficiency for each solute studied to gain insight into the retention mechanism. These studies help to understand the origin of stationary phase shape selectivity and the separation process in general. Based on these results, the molecular pictures at the stationary phase/solvent interface are proposed. The effect of pressurized solvent environments on two C18 phases is studied to obtain direct evidence for changes in stationary phase structure due to pressure. These changes are compared to effects of solvation relative to air in the same solvents. In addition, Raman spectral order indicators are identified for perdeuterated alkyl-containing system. This study provides a foundation for studying stationary phase structure in complex systems comprised of long alkyl-containing solutes. A further development of a new method is presented as well for synthesizing alkylsilane stationary phases with precisely controlled surface coverage by using a displaceable surface template monolayer of n-alcohol. A mechanism for this process is proposed based on the studies of n-alcohol concentration and chain length effect on the stationary phase surface coverage. The utility of these new stationary phases as chromatographic support is demonstrated. The shape selectivity for these new phases is comparable to or better than similar phases prepared by conventional methods.
Author: Lay Choo Tan
Publisher:
ISBN:
Category :
Languages : en
Pages : 628
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Author: Gokulakrishnan Srinivasan
Publisher:
ISBN: 9783832510565
Category :
Languages : en
Pages : 0
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The development of alkyl bonded stationary phases is one of the major factors, which lead to the growth of reversed-phase high performance liquid chromatography as the most popular mode of high-performance liquid chromatography. In such materials, the conformational order of the alkyl chain moieties is expected to be a major source for the efficiency and selectivity during chromatographic separations. Describing the alkyl chain conformational order on the molecular level is thus crucial for the understanding of such materials function in their respective chromatographic applications. In the present work FT IR and solid-state NMR spectroscopic techniques are employed to examine the conformational order and mobility of alkyl chain segments chemically attached to solid surfaces. The influence of the different solid supports, pressure, surface coverage, synthetic routes and solvents over the wider temperature range on the conformational order of the alkyl chains have been examined. Inspection of the FT IR data for the C30 SAMs reveals that the solid substrate plays a vital role for the actual conformational state of the attached alkyl chains. On investigating commercial DiamondBond-C18 phases, it is found that alkyl chains tethered to the graphite layer, exhibit a higher conformational order than those in conventional column materials. A comparative study reveals that C18 alkyl modified silica gels with higher surface coverage exhibit a higher conformational order compared to one with lower surface coverage. It was found that the C18 phases and solvents interact significantly, resulting in pronounced changes of the alkyl chain conformational order. A decrease in the conformational disorder is found on application of pressure to the stationary phase materials. The results derived from the present studies state that these aforementioned parameters have a strong influence on the conformational order and mobility of alkyl chains tethered to the inorganic metal oxides.
Author: Tina M. Mannschreck
Publisher:
ISBN:
Category : Chromatographic analysis
Languages : en
Pages : 136
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Author: Ante M. Krstulovic
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 316
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Book Description
A comprehensive problem-solving approach to reversed-phase high-performance liquid chromatography covering the theoretical aspects and practical information needed in diverse areas of research. Also reviews RPLC applications in the biomedical/biochemical field.
Author: Phyllis R. Brown
Publisher: CRC Press
ISBN: 1482289806
Category : Science
Languages : en
Pages : 678
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Book Description
"Volume 40 presents an authoritative selection of the best and most up-to-date research findings in separation science. Surveys recent developments in high performance-liquid (HPLC), reversed-phase liquid (RPLC), countercurrent (CCC), and micellar electrokinetic chromatography (MEKC)."
Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 726
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Author: Jun-Liang Lin
Publisher:
ISBN:
Category :
Languages : en
Pages :
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