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141.
Zusammenfassung Es wird eine rasche Methode zur Bestimmung von Magnesium in Aluminium und Aluminiumlegierungen beschrieben. Magnesium wird als CMAB-Oxin-Komplex mit Chloroform extrahiert und nach Rückschüttelung mit einer Boratpufferlösung spektralphotometrisch unter Verwendung von Calmagit als Reagens bestimmt.
Herrn Prof. Dr. W. Leithe danken wir für wertvolle Anregungen und Hinweise, der Direktion der Österreichischen Stickstoffwerke AG für die Erlaubnis zur Veröffentlichung. 相似文献
Summary A quick method is described for the determination of magnesium in aluminium and aluminium alloys. Magnesium is first separated as CMAB-oxine complex in chloroform and after back-extraction into a borate-buffer solution determined spectrophotometrically using Calmagite as reagent.
Herrn Prof. Dr. W. Leithe danken wir für wertvolle Anregungen und Hinweise, der Direktion der Österreichischen Stickstoffwerke AG für die Erlaubnis zur Veröffentlichung. 相似文献
142.
7-Substituted 4-hydroxycoumarins (2a-e) and 4-hydroxy-2-quinolones (2f-i) have been synthesized from the appropriate phenols or anilines and were converted to the enamines 3 using triethoxymethane and aniline. Condensation of 3 with nitriles 4a-h gave substituted 2H,5H-pyrano[3,2-c]benzopyran-2,5-diones (5a-r) or 2H,5H-pyrano[3,2-c]quinoline-2,5-diones (5s-x) , which exhibit both spontaneous and stimulated fluorescence with maxima between 418 and 549 nm. The marked influence of an electron withdrawing 3-substituent in 5 is demonstrated by the fluorescence spectra of 7a,b (synthesized from 2d,e and ethyl 3-oxobutyrate), whose maxima are sharply shifted to the blue as compared with compounds 21-r. 相似文献
143.
Harald Greger Otmar Hofer Andreas Werner 《Monatshefte für Chemie / Chemical Monthly》1985,116(2):273-277
In addition to the well known affinin [=spilanthol, (2E,6Z,8E)-deca-2,6,8-trienoic acid isobutylamide (1)], the corresponding 2-methyl-butylamide (2), and two new acetylenic alkamides were isolated fromSpilanthes oleracea L. by reversed phase medium pressure chromatography: (Z)-non-2-en-6,8-diynoic acid isobutylamide (3) and (Z)-dec-2-en-6,8-diynoic acid isobutylamide (4). The structures and their stereochemistries were elucidated by1H-NMR,13C-NMR (2 and3), MS, UV, IR, and CD (2). The chemotaxonomic significance of the distribution of alkamides within theCompositae tribeHeliantheae is briefly discussed.
Neue Amide ausSpilanthes oleracea (Kurze Mitteilung)
Zusammenfassung AusSpilanthes oleracea wurden neben dem seit langem bekannten Affinin [=Spilanthol, (2E,6Z,8E)-Deca-2,6,8-triensäureisobutylamid (1)] durch Umkehrphasen-Mitteldruckchromatographie das entsprechende 2-Methylbutylamid (2) und zwei neue acetylenische Alkamide isoliert: (Z)-Non-2-en-6,8-diinsäure-isobutylamid (3) und (Z)-Dec-2-en-6,8-diinsäure-isobutylamid (4). Die Strukturen und deren Stereochemie wurden mittels1H-NMR,13C-NMR (2 und3), MS, UV, IR und CD (2) aufgeklärt. Die chemotaxonomische Bedeutung der Verbreitung von Alkamiden innerhalb der Compositen-TribusHeliantheae wird kurz diskutiert.相似文献
144.
Monolithic capillary columns were prepared by copolymerization of styrene and divinylbenzene inside a 200 microm i.d. fused silica capillary using a mixture of tetrahydrofuran and decanol as porogen. Important chromatographic features of the synthesized columns were characterized and critically compared to the properties of columns packed with micropellicular, octadecylated poly(styrene-co-divinylbenzene) (PS-DVB-C18) particles. The permeability of a 60 mm long monolithic column was slightly higher than that of an equally dimensioned column packed with PS-DVB-C18 beads and was invariant up to at least 250 bar column inlet pressure, indicating the high-pressure stability of the monolithic columns. Interestingly, monolithic columns showed a 3.6 times better separation efficiency for oligonucleotides than granular columns. To study differences of the molecular diffusion processes between granular and monolithic columns, Van Deemter plots were measured. Due to the favorable pore structure of monolithic columns all kind of diffusional band broadening was reduced two to five times. Using inverse size-exclusion chromatography a total porosity of 70% was determined, which consisted of internodule porosity (20%) and internal porosity (50%). The observed fast mass transfer and the resulting high separation efficiency suggested that the surface of the monolithic stationary phase is rather rough and does not feature real pores accessible to macromolecular analytes such as polypeptides or oligonucleotides. The maximum analytical loading capacity of monolithic columns for oligonucleotides was found to be in the region of 500 fmol, which compared well to the loading capacity of the granular columns. Batch-to-batch reproducibility proved to be better with granular stationary phases compared to monolithic stationary phase, in which each column bed is the result of a unique column preparation process. 相似文献
145.
From solutions of chromium(III) perchlorate and periodic acid, single crystals of γ‐HIO3 were obtained and characterized by single‐crystal X‐ray diffraction, Raman spectroscopy and thermal analysis. The compound crystallizes in the orthorhombic crystal system, space group Pbca (a = 563.92, b = 611.10, c = 1507.16 pm). The structure is built up by dimers (HIO3)2, which are formed by hydrogen bonds. The crystals are metastable and transform into the stable modification, α‐HIO3, within a couple of weeks. 相似文献
146.
Woldegiorgis A von Kieseritzky F Dahlstedt E Hellberg J Brinck T Roeraade J 《Rapid communications in mass spectrometry : RCM》2004,18(8):841-852
The use of non-polar, small polymers as matrices for the analysis of low molecular weight compounds in polymer-assisted laser desorption/ionization mass spectrometry (PALDI-MS) is demonstrated. The matrices evaluated were either based on an oligothiophene or a benzodioxin backbone. Metallocenes, polycyclic hydrocarbons, a fluorosurfactant, and a subset of small organic compounds with various functionalities, served as model analytes. The mechanism of ionization charge transfer is discussed and ionization potentials for the matrices in the study have been estimated using density functional theory (DFT) calculations. Some of the results are possibly contradictory to the generally accepted limiting conditions for gas-phase charge-transfer reactions. These results are interpreted in the light of energy pooling. Also a new mass calibration procedure for the low-mass region in positive ion mode is presented, and some aspects of the ionization/desorption process leading to radical cations are studied. 相似文献
147.
Kremser L Brückner A Heger A Grunert T Buchacher A Josic D Allmaier G Rizzi A 《Electrophoresis》2003,24(24):4282-4290
The isoforms distribution of the glycoprotein antithrombin III (ATIII) derived from human plasma was investigated by means of isoelectric focusing (IEF) in polyacrylamide gels with immobilized pH gradients (IPG) and two-dimensional gel electrophoresis (2-DE) as well as capillary electrophoretic methods. It turned out that the presence of high concentrations of chaotropics (urea, thiourea) and zwitterionic detergents (3-[(3-cholamidepropyl)dimethylammonio]-1-propanesulfonate (CHAPS)) was decisive for attaining good resolution of the protein isoforms. Resolution by IPG-IEF was obtained with excellent reproducibility and pI differences down to 0.01 pH units could be distinguished. ATIII-alpha and ATIII-beta-fractions preseparated by heparin affinity chromatography showed an analogous but shifted spot pattern consisting each of one major and three minor isoforms. The main isoforms of ATIII-alpha and ATIII-beta exhibit pI values of 5.18 and 5.32, respectively, both values determined in the presence of high concentrations of urea. The pI difference of 0.14 pH units correspond to the effect of two sialic acids absent in ATIII-beta. The formation and occurrence of ATIII dimers and trimers turned out to be dependent on the sample preparation. The results obtained by 2-DE were compared with those of capillary zone electrophoresis (CZE) and capillary IEF (CIEF). Quantitative analysis regarding the CZE separated isoforms of plasma derived ATIII yielded a content of about 70% ATIII-alpha main isoform and about 6.6% of ATIII-beta. The pI values of ATIII determined by CIEF with internal calibration were in fair agreement with the pI values of the main isoforms achieved with 2-DE. 相似文献
148.
Rapp E Jakob A Schefer AB Bayer E Albert K 《Analytical and bioanalytical chemistry》2003,376(7):1053-1061
A mixture of unsaturated fatty acid methyl esters was separated with a new splitless capillary set-up. With the employed apparatus configuration different capillary separation techniques such as capillary high-performance liquid chromatography (cHPLC), capillary electrochromatography (CEC) and pressurized capillary electrochromatography (pCEC) could be applied. The detection and identification of the sample compounds were accomplished by hyphenating these capillary separation techniques with nuclear magnetic resonance (NMR) spectroscopy using a novel configuration of the detection capillary set-up. Using modified electrokinetically driven separation techniques, the electric field was applied solely across the separation column. With this improved interface for capillary liquid chromatography-NMR on-line coupling, the stereochemical assignment of the cis and trans configuration of unsaturated fatty acids could be easily accomplished. Finally, the results of cHPLC-NMR, CEC-NMR and pCEC-NMR coupling experiments were compared.Dedicated to Professor Günter Häfelinger on the occasion of his 65th birthday 相似文献
149.
Focant JF Reiner EJ Macpherson K Kolic T Sjödin A Patterson DG Reese SL Dorman FL Cochran J 《Talanta》2004,63(5):1231-1240
Comprehensive two-dimensional gas chromatography with isotope-dilution time-of-flight mass spectrometry (GC × GC-IDTOFMS) was used to measure polychlorinated dibenzo-p-dioxin (PCDD), polychlorinated dibenzofuran (PCDF), and coplanar polychlorinated biphenyl (cPCB) concentrations in ash, sediment, vegetation, and fish samples. The GC × GC capability was achieved by using a quad jet, dual stage, thermal modulator. Zone compression of the GC peaks from modulation resulted in a significant increase of the signal intensity over classical GC-IDTOFMS. The GC × GC column set used an Rtx-Dioxin 2 phase as the first dimension (1D) and an Rtx-500 as the second dimension (2D). The chromatographic separation of the 17 PCDD/Fs and the 4 cPCBs was attained in 1D except for 2,3,7,8-TCDD and CB126 for which deconvoluted ion currents (DIC) were required to be reported separately. The Rtx-500 phase separated the bulk matrix interfering compounds from the target analytes in 2D. The instrumental limit of detection (iLODs) was 0.5 pg for 2,3,7,8-TCDD. The calibration curves showed good correlation coefficients for all the compounds investigated in the concentration range of 0.5–200 pg. GC × GC-IDTOFMS results compared favorably to those from conventional isotope-dilution one-dimensional gas chromatography-high resolution mass spectrometry (GC-IDHRMS). The comprehensive mass analysis of the TOFMS further permitted the identification of other contaminants of concern in the samples. 相似文献
150.