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H. Brindle 《Analytical and bioanalytical chemistry》1938,113(1-2):72-72
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Four new stationary phases for HPLC were prepared by modifying silica gel with a trifrnctional aminoalkyl silane. A conjugated π-electron system was linked to the amino group either directly or with a carboxylic anhydride as a spacer in between. Characterization and dynamic measurements of the new stationary phases were performed by solid state NMR spectroscopy. The results of the 29si and 13C CP/MAS techniques were compared with the recently developed 1H MAS-only technique. Despite strong homonuclear dipole-dipole interactions it was possible to obtain well resolved 1H MAS spectra of those stationaru phases with a high degree of crosslinking. Limited mobility of the aromatic ligand fragments is common for all examined stationaryu phases. The chromatographic properties of the new phases were tested by their ability tio sepatate a mixture of eight PAHS. It could be shown that the π-π interaction mechanism is responsible for the separation of the eight PAHs, because the elution order of the PAHs did not changem despite the use of both a nonpolar mobile phase (n-heptane) and a polar mobile phase (methanol/ water mixture). 相似文献
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Zhou SN Reiner EJ Marvin CH Helm PA Brindle ID 《Rapid communications in mass spectrometry : RCM》2011,25(3):443-448
Although the two flame retardants 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH) and 1,2,5,6-tetrabromocyclooctane (TBCO) have been widely used, a selective instrumental method of analysis for these compounds has not been developed to date. In this study, we demonstrate the feasibility to utilize liquid chromatography/tandem mass spectrometry (LC/MS/MS) for the separation and analysis of α- and β-TBCO and α-, β-, γ-, and δ-TBECH. Acetone was initially used in a tetrahedron solvent system for LC optimization. A simple isocratic elution allowed near-baseline separation of these compounds. Different ionization approaches and mechanisms were investigated. The mass spectrometric transition of [M + O(2)](-) => Br(-) (459.8 => 78.9) was a selective detection method for the target analytes. Good instrument detection limits (5 pg for γ-/δ-TBECH, 125 pg for α-/β-TBECH, and 30 pg for α-/β-TBCO with 2.0 μL injection) were obtained. Excellent linearity up to 50 ng/μL (R(2) >0.999) was also achieved. This method has been applied to environmental samples (surface water) for screening purposes with recoveries ranging from 76-92% (CV%: 5-8%). This method shows significant improvement over previous methods. 相似文献
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Summary A micromanipulator is described which has been specially designed to meet the requirements of chemical work on the microgram scale. The instrument carries a micropipette controlled by a micrometer syringe, and manipulates this in relation to the vessels, which are carried on the rotating mechanical stage of a low-power microscope.
With 2 figures. 相似文献
Zusammenfassung Ein Mikromanipulator für die speziellen Bedürfnisse der chemischen Untersuchung von Gammamengen wird beschrieben. Das Instrument trägt eine Mikropipette, die mit Hilfe einer Mikrometer-Injektionsbürette kontrolliert wird. Diese Pipette wird mittels des Manipulators in die Reaktionsgefäße eingeführt, die auf dem drehbaren Tisch eines Mikroskopes mit schwacher Vergrößerung angebracht werden.
Résumé On décrit un micromanipulateur spécialement destiné à faire face aux besoins du travail chimique à l'échelle du microgramme. L'instrument porte une micropipette controlée par une seringue micrométrique et actionne celle-ci par rapport aux vases qui sont portés par la plateforme tournant mécaniquement d'un microscope de faible puissance.
With 2 figures. 相似文献
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Back Cover: Imaging Glycosylation In Vivo by Metabolic Labeling and Magnetic Resonance Imaging (Angew. Chem. Int. Ed. 4/2016)
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Dr. André A. Neves Dr. Yéléna A. Wainman Dr. Alan Wright Dr. Mikko I. Kettunen Dr. Tiago B. Rodrigues Sarah McGuire Dr. De‐En Hu Flaviu Bulat Dr. Simonetta Geninatti Crich Dr. Henning Stöckmann Dr. Finian J. Leeper Prof. Kevin M. Brindle 《Angewandte Chemie (International ed. in English)》2016,55(4):1566-1566
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Computer simulations based on Discrete Element Method have been performed in order to investigate the influence of interparticle interactions on the kinetics of self-assembly and the mechanical strength of nanoparticle aggregates.Three different systems have been considered.In the first system the interaction between particles has been simulated using the JKR (Johnson,Kendall and Roberts) contact theory,while in the second and third systems the interaction between particles has been simulated using van der Waals and electrostatic forces respectively.In order to compare the mechanical behaviour of the three systems,the magnitude of the maximum attractive force between particles has been kept the same in all cases.However,the relationship between force and separation distance differs from case to case and thus,the range of the interparticle force.The results clearly indicate that as the range of the interparticle force increases,the self-assembly process is faster and the work required to produce the mechanical failure of the assemblies increases by more than one order of magnitude. 相似文献
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M. Pursch R. Brindle A. Ellwanger L. C. Sander C. M. Bell H. Hndel K. Albert 《Solid state nuclear magnetic resonance》1997,9(2-4):191-201
Stationary interphases with long n-alkyl chains (n = 18, 22, 30, 34) have been examined by solid-state NMR spectroscopy. The determination of the silane functionality and the degree of cross-linking of silane ligands on the silica surface was performed by 29Si CP/MAS NMR spectroscopy. High-speed 1H MAS and 13C CP/MAS NMR spectroscopy were utilized to assess alkyl chain order and mobility of the different bonded phases. For this purpose, 1H NMR line widths and 13C chemical shifts have been evaluated. It is shown that stationary phase order and rigidity increase with alkyl chain length. In addition, the temperature-dependent trans/gauche conformational change occurs at higher temperatures for a polymeric C34 phase compared with a C30 sorbent. This behaviour is discussed in the context of previously reported Chromatographic (HPLC) shape selectivity differences. 相似文献