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排序方式: 共有239条查询结果,搜索用时 453 毫秒
1.
R. Pietsch 《Fresenius' Journal of Analytical Chemistry》1957,155(3):189-194
Zusammenfassung Es wird über die Möglichkeit einer Bestimmung des Vanadat-Ions mit Phenarsazinsäure berichtet. Vanadat fällt mit dem Reagens in saurem Medium bei pH 2 als hellbrauner flockiger Niederschlag quantitativ aus, wenn ein mehr als dreifacher molarer Überschuß an Phenarsazinsäure angewendet wird. Die Bestimmung des Vanadiums im gebildeten Niederschlag erfolgt maßanalytisch. Über einige Trennungsmöglichkeiten wird berichtet. 相似文献
2.
Analytical and Bioanalytical Chemistry - Es wird eine neue extraktive Trennungsmethode für Uran beschrieben. Mit Hilfe einer Lösung von Triphenylarsinoxid in Chloroform lassen sich... 相似文献
3.
R. Pietsch 《Mikrochimica acta》1955,43(5-6):1019-1025
Zusammenfassung Die qualitative Fällung von Metallionen mit den drei isomeren o-, m- und p-Nitrophenylarsinsäuren wird beschrieben und auf Unterschiede der ph-Werte des Fällungsbeginnes hingewiesen. Die Beeinflussung des Fällungsbeginnes durch die Stellung der Nitrogruppe wird hervorgehoben.
Summary The precipitation of metal ions by means ofo-, m-, andp-nitrophenyl arsonic acids is described. The differences of the pH values of the start of the precipitation are pointed out. The effect of the position of the nitro group on the beginning of the precipitation is stressed.
Résumé On décrit la précipitation qualitative d'ions métalliques par les trois isomèreso., m. etp. de l'acide nitrophénylarsonique et l'on donne des indications concernant les différences de valeur du ph lors du commencement de précipitation. On met en évidence l'influence de la position du groupe nitro sur le commencement de précipitation.相似文献
4.
S. A. Stepanov U. Pietsch G. T. Baumbach 《Zeitschrift für Physik B Condensed Matter》1995,96(3):341-347
A method for computation of X-ray grazing-incidence diffraction (GID) in multilayers and superlattices is presented. The method is based on X-ray dynamical diffraction theory and a matrix from a boundary equations and provides a simple numerical solution of the problem. The application of the method to simulating GID measurements taken from A1As/GaAs superlattice (20 periods of 14.6 nm A1As and 6.8 nm GaAs) demonstrates the principal validity of the theory. A perfect matching between the theory and the experiment requires the real-structure effects of sample to be taken into account. 相似文献
5.
Determination of aliphatic and alicyclic amines in water by gas and liquid chromatography after derivatization by chloroformates 总被引:1,自引:0,他引:1
J. Pietsch S. Hampel W. Schmidt H.-J. Brauch E. Worch 《Fresenius' Journal of Analytical Chemistry》1996,355(2):164-173
Two new methods were developed for the analysis of aliphatic (n-propylamine, pentylamine, hexylamine, heptylamine, octylamine) and alicyclic (pyrrolidine, morpholine, piperidine, piperazine) amines in water samples after derivatization and liquid-liquid-extraction. The carbamate-derivatives formed were determined by GC/MS (trichloroethyl carbamates) as well as by HPLC/fluorescence detection (9-fluorenylmethyl carbamates) in a concentration range between 0.05 and 1.0 g/l suitable for drinking water analysis. Applications to German rivers and sewage plants show that both new methods produce corresponding results in analysing aliphatic and alicyclic amines in surface waters as well as in waste water samples. 相似文献
6.
7.
J. Pietsch W. Schmidt F. Sacher S. Fichtner H.-J. Brauch 《Fresenius' Journal of Analytical Chemistry》1995,353(1):75-82
The main components of organic micro pollution regularly found in the river Elbe, belong to the wide spectrum of pesticides, nitro and chloro benzenes and the chelating agents, especially ethylenediaminetetraacetic acid (EDTA). The level of organic micro pollution with pesticides and the other organic micro pollutants in the upper and middle reaches of the river Elbe between Schmilka and Wittenberge was determined over a period of nearly three years. Four sample preparation methods (SPE: solidphase extraction and LLE: liquid-liquid extraction both with and without derivatization) have been used to analyze a wide spectrum of pesticides with different polarities by GC/ECD, NPD and MS. The pesticide pollution caused by the triazines decreases significantly from 0.35 g/l (mean value) in 1992 up to 0.15 g/l (mean value) in 1994. The correlation with the river water flow shows the diffuse character of the triazine input. In the last year of the pesticide screening a change to the more polar substances such as phenoxyalkanoic acid and nitrophenol pesticides as well as chloralkanoic acid pesticides have been noticed. The origin of trichloroacetic acid (TCA) can be explained by the waste influence, supported by the good correlation of the TCA course with the chloroform concentrations determined. 相似文献
8.
Malcolm W. R. Reed T. Jeffery Wieman Karola W. Doak Catherine G. Pietsch Dale A. Schuschke 《Photochemistry and photobiology》1989,50(3):419-423
Photodynamic therapy (PDT) of malignant tumours may involve the interruption of tumor and peritumor microcirculation. We have studied the effect of light activation of the photosensitizing drug dihematoporphyrin ether (DHE) on rat subcutaneous arterioles and the modulation of these effects by cyclooxygenase inhibitors indomethacin and acetyl salicylic acid (ASA). Animals received DHE 48 h prior to light activation and additionally either indomethacin, ASA or saline 3 h prior to treatment. Light activation (630 nm, 60 J/cm2) resulted in a significant reduction to 62 +/- 2% SEM of initial blood flow. This effect was inhibited by ASA (98 +/- 8% SEM) and indomethacin (87 +/- 8% SEM). Results from the administration of various doses of both compounds indicate that this inhibition is dose related. The data presented here show that PDT causes a significant reduction in blood flow in normal arterioles and that this effect was inhibited by ASA and indomethacin indicating that prostaglandins or thromboxane A2 may play an important role in the microvascular response to PDT. 相似文献
9.
Tsirelson Vladimir Abramov Yury Zavodnik Valery Stash Adam Belokoneva Elena Stahn Jochen Pietsch Ullrich Feil Dirk 《Structural chemistry》1998,9(4):249-254
The critical points in the model electron density distributions of LiF, NaF, NaCl, and MgO crystals, constructed from accurate X-ray diffraction data, are determined. For LiF and MgO they are compared with those obtained from a Hartree–Fock electron density calculation. Both experiment and theory show the same type of critical points on the bond lines. The topological features in areas between structural units, where the electron density is low and near-uniform, turn out to be model dependent and cannot be established well with the data available. Topological analysis of procrystals (hypothetical systems consisting of spherical atoms or ions placed on the same sites as atoms in real crystal) show that (3, –1) critical points, usually connected with bonding interaction, are observed on interatomic lines in these nonbonded systems as well. 相似文献
10.
Markus Pietsch Martin Nieger Michael Gütschow 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(3):o147-o151
The title compounds, tert‐butyl 6‐benzyl‐2‐(3,3‐diethylureido)‐4,5,6,7‐tetrahydrothieno[2,3‐c]pyridine‐3‐carboxylate, C24H33N3O3S, (I), 7‐benzyl‐2‐diethylamino‐5,6,7,8‐tetrahydro‐3‐oxa‐9‐thia‐1,7‐diazafluoren‐4‐one, C20H23N3O2S, (II), and N‐(7‐benzyl‐4‐oxo‐5,6,7,8‐tetrahydro‐4H‐3,9‐dithia‐1,7‐diazafluoren‐2‐yl)benzamide, C23H19N3O2S2, (III), form monoclinic crystal systems. In (I) and (II), the molecules are linked into a three‐dimensional framework by weak intermolecular C—H⋯O=C hydrogen bonds, whereas in (III) stronger intermolecular N—H⋯O=C interactions are observed. The conformation of (I) is further stabilized by an intramolecular N—H⋯O=C hydrogen bond, which effects the planarity of the ureidothiophenecarboxylate moiety. 相似文献