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61.
Zusammenfassung Die Reaktionsparameter der Umsetzung von DANS-Cl mit den Catecholaminen Adrenalin, Noradrenalin und Dopamin wurden systematisch untersucht und für eine gemeinsame Derivatisierung optimiert: pH 8–9, 40% Wasser im Aceton/Wasser-Gemisch, 2 fach stöchiometrischer Überschuß an DANS-Cl, 20 min bei 40° C. Die DANS-Catecholamine lassen sich adsorptions- und reverse-phase-chromatographisch trennen, wobei für die Zusammensetzung der mobilen Phasen kurze Analysenzeiten mit optimaler Trennung angestrebt wurden. Vor- und Nachteile der beiden hochdruck-flüssigkeits-chromatographischen Verfahren werden gegenübergestellt.
High-pressure liquid chromatography of the catecholamines as DANS-derivates — Derivatization and separation
The parameters of the reaction of DANS-Cl with the catecholamines adrenaline, noradrenaline, and dopamine were studied systematically and optimized for an simultaneous derivatization: pH 8–9, 40% water in an acetone water mixture, twofold stoichiometric excess of DANS-Cl, 20 min at 40° C.The DANS-catecholamines are separable by adsorption and reverse-phase chromatography. Short analytical times with optimal separation were intended for the composition of the mobile phases. Advantages and disadvantages of the two high-pressure liquid Chromatographic methods are discussed.相似文献
62.
Rappolt M Amenitsch H Strancar J Teixeira CV Kriechbaum M Pabst G Majerowicz M Laggner P 《Advances in colloid and interface science》2004,111(1-2):63-77
In this work, we report on recent investigations, both on the global and on the local molecular architecture of supported phospholipid model membranes. A brief theoretical introduction explains how global structural information on supramolecular lipid ensembles can be retrieved from surface X-ray diffraction measurements as well as how spin-label electron paramagnetic resonance spectroscopy (EPR) provides complementary information on the local environment of probe molecules. The combination of especially designed X-ray cells with the technique of small- and wide-angle X-ray surface scattering makes it possible to explore various fields of lipid research and its applications. Examples for different physico-chemical conditions are presented: (i) in situ chemistry under excess of water conditions demonstrating how solid-supported lipid films sense salinity, (ii) the 3D electron density reconstruction of a vesicle-fusion intermediate under controlled humidity, and (iii) complementary temperature and pressure effects on oriented phospholipid samples. Further, special attention has been given to the influence of different film preparation techniques with respect to quality and the defect structure manifestation. To resolve the proportions and local properties of defects in a hydrated lipid-deposited surface, spin-label EPR was applied. The results from 9.6 GHz EPR as well as from 1.2 GHz EPR suggest the alignment to be in the range between 30% and 80%. In addition, slow time-dependent EPR measurements point to nano-structural rearrangements due to water flow and reduction of alignment quality. 相似文献
63.
Hähner G Zwahlen M Caseri W 《Langmuir : the ACS journal of surfaces and colloids》2005,21(4):1424-1427
Self-assembled alkyl chain based monolayers on mica are important for industrial and technological processes since they can be employed for an organic modification of the inorganic substrate. The conformational structure and orientational order of the films determine the interaction of the modified substrate with the environment and the chemical character and stability of its surface. We have studied the conformational order in ion exchanged dialkylammonium monolayers adsorbed on mica depending on the length of the alkyl chains systematically with near-edge X-ray absorption fine structure spectroscopy (NEXAFS). In addition, films were characterized by water contact angle measurements. The experimentally determined average tilt angles of the chains are discussed in terms of the degree of order. It was found that the absolute number of gauche defects in the films increases with decreasing chain length. 相似文献
64.
Dieter Seebach Georg Jaeschke Arkadius Pichota Laurent Audergon 《Helvetica chimica acta》1997,80(8):2515-2519
Two simple thiols derived from the parent TADDOL, α,α,α′,α′ tetraphenyl-2,2-dimethyl-1,3-clioxolan-4,5-dimethanol, are used to prepare Cu1 complexes C and D to catalyze (0.05 equiv.) 1,4-additions of Grignard reagents RMgCl to cyclic enones with enantioselectivities which are comparable to or better than previously reported (enantiomer ratios up to 92:8). 相似文献
65.
The present-day position in the field of polymeric catalysts is outlined. The following selected groups of polymeric catalysts are discussed: synthetic hydrolases, immobilized enzymes, phase-transfer catalysts, nucleophilically active bases, polymers with conjugated π-systems, photosensitizers, polymers as carriers for catalytically active metals or ions, and immobilized homogeneous catalysts. Polymeric catalysts have the following valuable properties: insoluble polymeric catalysts are readily separable from reaction solutions and can often be re-used without loss of activity; a hydrophobic matrix protects the organometallic active center from deactivation by oxygen and water; by fixation of finely divided metals on an ion exchanger, multistage reactions may be effected successively in one reactor. Polymeric carriers may influence the catalytic properties; for example, in the case of immobilized enzymes on polyionic carriers the pH of the activity maximum may be shifted. 相似文献
66.
Hege Rebecka Johansen Christian Thorstensen Tyge Greibrokk Georg Becher 《Journal of separation science》1993,16(3):148-152
On-line coupled supercritical fluid extraction and gas chromatography (SFE-GC) has been utilized for the determination of PCBs and other organochlorine compounds in human milk and blood serum. The procedure involved preconcentration of the sample on C18-silica sorbent in an extraction cell: after precipitation of the proteins up to 20 ml of human milk was concentrated on 0.5 g of sorbent. Serum (up to 5 ml) was applied to the C18 material without pretreatment. Basic alumina was utilized as a selective adsorbent for lipids in the on-line SFE-GC system. The method was used to analyze milk and serum spiked with 0.5 and 10 ng of Aroclor 1260 and the results compared with those obtained by liquid–liquid extraction of serum. 相似文献
67.
Werner Georg Nowak 《Journal of Number Theory》1984,19(2):254-262
It is proved that (for every ε > 0) (where {·} denotes the fractional part and Bk the Bernoulli polynomial of order k) under the suppositions that k ≥ 2 and 2a ? 1 ≥ b ≥ 1. If (1) were true for k = 1, a = b = 0, then Piltz' divisor problem (for n = 3) would be readily solved. This is an analog to a conjecture formulated by S. Chowla and H. Walum in 1963 and settled in the affirmative (under suitable suppositions) quite recently by S. Kanemitsu and R. Sita Rama Chandra Rao. 相似文献
68.
Wolfgang Hnle Walter Schmettow Karl Peters Jen‐Hui Chang Hans Georg von Schnering 《无机化学与普通化学杂志》2004,630(12):1858-1862
The novel ternary polyphosphides M4P21I (M = K, Rb) have been synthesized from the elements in single crystalline form, representing further examples for the formation of mixed crystals between simple salts and binary phosphides. They form as ruby‐red platelets and dark‐red prisms, respectively, and are only slightly sensitive to moisture and oxygen. The compounds are isotypic (Ccmm (no 63); Z = 4; oP104; K4P21I: a = 12.853Å; b = 21.795Å; c = 9.748Å; 1168 hkl, R = 0.033; Rb4P21I: a = 13.281Å; b = 21.868Å; c = 9.771Å; 777 hkl, R = 0.053) and feature corrugated 2D networks formed from two different types of polymerized P7 units. The networks form large cavities filled by M+ and I‐ ions. Zigzag chains of condensed trigonal M6 prisms, centered by the I‐ anions, separate the polyphosphide nets. The mean homoatomic P‐P bond length (d = 2.216Å) corresponds to a P‐P single bond. However, the individual P‐P distances vary with position and function (2.126 ‐ 2.247Å) and these are compared with those of the isolated P21‐3 anion. 相似文献
69.
Werner Georg Nowak 《manuscripta mathematica》1984,49(2):195-205
Let A(x) denote the number of lattice points in the circle u2+v2x and define as the infimum of all reals for which
. The objective of this paper is to show that 35/108 which improves upon all previously known results. This estimate is an immediate consequence of a surprisingly easy generalization of KOLESNIK's work on Dirichlet's divisor problem to divisor functions with respect to arithmetic progressions. 相似文献
70.
Wieslaw Wojnowski Barbara Becker Karl Peters Eva-Maria Peters Hans Georg von Schnering 《无机化学与普通化学杂志》1987,553(10):287-292
Structure of Pentaphenyldisilane For the first time Pentaphenyldisilane was prepared by Gilman and Goodman. It is produced by the reaction of Ph3SiLi with Ph2ClSiH. The crystal structure presents an ideally staggered conformation. The distance d(Si? Si) = 235.7 pm corresponds to a normal single bond length. This emphasizes the complete relief of the central Si? Si bond by the insertion of only one hydrogen atom. 相似文献