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A high-performance liquid chromatographic method for the determination of R- and S-prenylamine in human plasma and urine is described. It involves a two-step liquid-liquid extraction of prenylamine from biological material and preparation of diastereomeric urea derivatives with R-(-)-naphthylethyl isocyanate, a chiral fluorescence marker. Separation and quantitation of the diastereomeric prenylamine derivatives are carried out by a reversed-phase high-performance liquid chromatographic system with fluorimetric detection. The limit of determination is less than 2 ng of enantiomer per ml of urine and less than 1 ng of enantiomer per ml of plasma. A preliminary kinetic study on one healthy volunteer who had received a single oral dose of racemic prenylamine (100-mg film tablet) showed distinctly higher plasma and urine concentrations of the R-enantiomer. 相似文献
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The separation of racemic benoxaprofen into the two benoxaprofen enantiomers by preparative high-performance liquid chromatography and the application of the activated enantiomers as derivatization reagents for the simultaneous stereoselective determination of chiral amines in biological material is described. Activated (+)- and (-)-benoxaprofen are both shown to be very sensitive and stable chiral fluorescence markers, applicable to thin-layer chromatography as well as to high-performance liquid chromatography. 相似文献
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M. M. Shehata B. Scholten I. Spahn H. H. Coenen S. M. Qaim 《Journal of Radioanalytical and Nuclear Chemistry》2011,287(2):435-442
A method for the separation of no-carrier-added arsenic radionuclides from the bulk amount of proton-irradiated GeO2 targets as well as from coproduced radiogallium was developed. The radionuclides 69Ge and 67Ga produced during irradiation of GeO2 were used as tracers for Ge and Ga in the experiments. After dissolution of the target the ratio of As(III) to As(V) was
determined via thin layer chromatography (TLC). The extraction of radioarsenic by different organic solvents from acid solutions
containing alkali iodide was studied and optimized. The influence of the concentration of various acids (HCl, HClO4, HNO3, HBr, H2SO4) as well as of KI was studied using cyclohexane. The optimum separation of radioarsenic was achieved using cyclohexane with
4.75 M HCl and 0.5 M KI and its back-extraction with a 0.1% H2O2 solution. The separation leads to high purity radioarsenic containing no radiogallium and <0.001% [69Ge]Ge. The overall radiochemical yield is 93 ± 3%. The practical application of the optimized procedure in the production
of 71As and 72As is demonstrated and batch yields achieved were in the range of 75–84% of the theoretical values. 相似文献
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Christoph Spahn Florian Hurter Mathilda Glaesmann Christos Karathanasis Marko Lampe Mike Heilemann 《Angewandte Chemie (International ed. in English)》2019,58(52):18835-18838
Photobleaching is a major challenge in fluorescence microscopy, in particular if high excitation light intensities are used. Signal‐to‐noise and spatial resolution may be compromised, which limits the amount of information that can be extracted from an image. Photobleaching can be bypassed by using exchangeable labels, which transiently bind to and dissociate from a target, thereby replenishing the destroyed labels with intact ones from a reservoir. Here, we demonstrate confocal and STED microscopy with short, fluorophore‐labeled oligonucleotides that transiently bind to complementary oligonucleotides attached to protein‐specific antibodies. The constant exchange of fluorophore labels in DNA‐based STED imaging bypasses photobleaching that occurs with covalent labels. We show that this concept is suitable for targeted, two‐color STED imaging of whole cells. 相似文献
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Ekkehard Fluck Manfred Spahn Gernot Heckmann Horst Borrmann Axel Obermeyer 《Heteroatom Chemistry》1991,2(5):593-599
1,1,3,3 - Tetrakis(dimethylamino) - 1λ5,3λ5 - diphosphete, 1 , reacts with cyanoformic acid methyl ester to form two isomers of the title compound 2 . Properties, NMR, mass, and IR spectra of 2 , as well as the molecular and crystal structure of the E isomer of 2 , are described and discussed. 相似文献
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A flow-through cell with integrated hanging mercury drop electrode for voltammetric, inverse voltammetric, adsorptive voltammetric, and chronoamperometric methods is described. HMDE droplets are automatically formed and renewed. By optimizing the flow-channel the sensitivity could be increased approximately five times in comparison with batch methods using the same deposition conditions.Dedicated to Professor Dr. Rolf Neeb on the occasion of his 65th birthday 相似文献
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A. Breakstone C. D. Buchanan R. Campanini H. B. Crawley G. M. Dallavalle M. M. Deninno K. Doroba D. Drijard F. Fabbri A. Firestone H. G. Fischer H. Frehse W. Geist G. Giacomelli R. Gokieli M. Gorbics P. Hanke M. Heiden W. Herr P. G. Innocenti E. E. Kluge J. W. Lamsa T. Lohse W. T. Meyer G. Mornacchi T. Nakada M. Panter A. Putzer K. Rauschnabel F. Rimondi R. Sosnowski J. Spahn M. Szczekowski O. Ullaland D. Wegener 《Zeitschrift fur Physik C Particles and Fields》1984,23(1):9-18
The density of charged particles near a single highp T trigger particle in proton-proton collisions has been studied with the SFM detector at the CERN-ISR. It is shown that:—the secondaries cluster in a jet-like manner about the trigger particle; —the momentum distributions in this trigger jet can be unambiguously separated from the spectator background distributions;—the momentum distributions in this trigger jet can be unambiguously separated from the spectator background distributions;—the momentum component transverse to the jet direction is exponentially damped;—the width of the transverse distributions increases with the momentum component along the jet;—the fractional longitudinal momentum density depends strongly on the trigger transverse momentum and scales with \(x_T = {{2p_T } \mathord{\left/ {\vphantom {{2p_T } {\sqrt s }}} \right. \kern-0em} {\sqrt s }}\) . All these findings support the hard constituent scattering origin of highp T hadrons. 相似文献
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W. Ebeling H. Hache M. Spahn 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(2):265-272
Applying Gibb's geometrical methods to the thermodynamics of H-plasmas we explore the landscape of the free energy as a function
of the degrees of ionization and dissociation. Several approximations for the free energy are discussed. We show that in the
region of partial ionization/dissociation the quantum Debye-Hückel approximation (QDHA) yields a rather good but still simple
representation which allows to include magnetic field and fluctuation effects. By using relations of Onsager-Landau-type the
probability of fluctuations and ionization/dissociation processes are described. We show that the degrees of ionization/dissociation
are probabilistic quantities which are subject to a relatively large dispersion. Magnetic field effects are studied.
Received 10 September 2002 / Received in final form 26 November 2002 Published online 11 February 2003 相似文献