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71.
Günter Ehrlich Thomas Nestler Rainer Voigtmann Willi Moldenhauer 《Mikrochimica acta》1989,98(4-6):249-258
To compare concentration profiles in solids in an objective manner, a multi-dimensional generalization of the comparison of two means by Student'st-test is proposed. The approach is based on piecewise modelling the profiles using rougha priori information, estimating the model parameters and their covariance matrix and comparing the estimated parameters by use of multidimensional test variables. The piecewise modelling is treated in the most important cases in such a way that the partial functions are straight lines or cubic polynoms (splines) with continuity at all knots in each case. It enables us to compare whole profiles as well as the most relevant parts of them. Two ways of estimating the covariance matrix as a generalization of the variance estimation are discussed. The approach is useful for any kind of line profiles if rough information on the profile type is available. As an example SIMS depth-profiles of aluminum obtained from thin-layer systems after different technological heat treatments are considered. These profiles are modeled by three straight lines. 相似文献
72.
A solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS) sampling and analysis method was developed for bis(diisopropylaminoethyl)disulfide (a degradation product of the nerve agent VX) in soil. A 30-min sampling time with a polydimethylsiloxane-coated fiber and high temperature alkaline hydrolysis allowed detection with 1.0 microg of VX spiked per g of agricultural soil. The method was successfully used in the field with portable GC-MS instrumentation. This method is relatively rapid (less than 1 h), avoids the use of complex preparation steps, and enhances analyst safety through limited use of solvents and decontamination of the soil before sampling. 相似文献
73.
Gert Brandl Fritz Kastner Rainer Fritsch Herbert Zinner Albrecht Mannschreck 《Monatshefte für Chemie / Chemical Monthly》1992,123(11):1059-1069
Summary A procedure is described which serves to measure circular dichrograms () on line during stops of flow in liquid chromatography. Since the concentration of substrate in the spectrometer cell during the stop is not known, the differential absorption coefficients are calculated from the experimental differential absorbances A by means of UV absorption (i. e. photomultiplier voltage) data. Verifications of the procedure are obtained by its application to three substrates (Table 1), the () spectra of which were known. The present on-line technique is compared with a corresponding off-line method.The N,N-dimethylthiobenzamides1 and2 as well as the 9,10-phenanthrenequinone7 consist of interconvertible enantiomers because their planar states are destabilized by steric overcrowding of groups. The unknown dichrograms () of1, 2 and7 are obtained (Figs. 2 and 4) and discussed with reference to the helicities of these molecules.In memory of the late Professor Dr. Dr. h. c. Günther Snatzke. 相似文献
74.
75.
Rahimipour S Litichever-Coslovsky N Alaluf M Freeman D Ehrenberg B Weiner L Mazur Y Fridkin M Koch Y 《Photochemistry and photobiology》2005,81(2):250-258
A combination of light, oxygen and a photosensitizer is used to induce death of cancer cells by photodynamic therapy. In this study, we have synthesized several new methyl helianthrone derivatives and compared their phototoxicity with that of hypericin. In contrast to hypericin, methyl helianthrones are soluble in aqueous solutions and have a broad range of light absorbance, which allows the use of polychromatic light. Structural modifications of methyl helianthrone demonstrated that substitution of hydrogen atoms of methyl helianthrone at Positions 2 and 5 with Br atoms or methylation of its phenolic hydroxyls, significantly increases the corresponding singlet oxygen quantum yield and their phototoxicity toward alphaT3-1, M2R and LNCaP cells. The phototoxicity of some of these compounds was similar to that of hypericin. Methyl helianthrones, like hypericin, accumulated mainly in the perinuclear region as evident by confocal microscopy. Irradiation of cells pretreated with methyl helianthrone derivatives generates intracellular reactive oxygen species and lipid free radicals, as shown by a fluorescentic probe and electron paramagnetic resonance methods, respectively. The phototoxicity of these methyl helianthrones as well as their ability to oxidize membrane lipids were significantly decreased on addition of specific Type-II inhibitors, suggesting the involvement of singlet oxygen as the main oxidant. 相似文献
76.
Zusammenfassung Auf Grund systematischer Untersuchungen des Verhaltens von Uran in verschiedenen wäßrig-organischen, Tri-n-octylphosphinoxid (TOPO) enthaltenden Lösungsmittelsystemen gegenüber verschiedenen Anionenformen des stark basischen Anionenaustauschers Dowex 1, X 8 wurde eine Methode zur Abtrennung des Urans entwickelt. Bei diesem Verfahren wird das Uran aus einer ascorbin-säurehaltigen, 1-n salzsauren Lösung mit 0,1-m TOPO in Diäthyläther extrahiert und aus einem Gemisch aus 50 Vol. % Äther (0,1-m an TOPO), 45 Vol. % Methylglykol und 5 Vol. % 12-n Salzsäure am Ionenaustauscher (Chloridform) adsorbiert. Nach Elution mit 1-n Salzsäure wird das Uran entweder fluorimetrisch oder spektrophotometrisch nach der Thiocyanatmethode bestimmt. Mit diesem Anionenaustauschverfahren ist eine Abtrennung des Urans von allen, seine fluorimetrische oder spektrophotometrische Bestimmung störenden Ionen und auch vom TOPO selbst möglich. Besonders wurde auf die spektrophotometrische Bestimmung des Urans bei Anwesenheit großer Molybdänmengen eingegangen und eine Methode zur Abtrennung dieses Elementes entwickelt.
Determination of small amounts of uranium after concentrating through extraction and anionic exchange in a solvent agent system containing tri-n-octylphosphine oxide
Summary A method has been developed for the separation of uranium that is based on systematic studies of the behavior of uranium in various water-organic solvent systems containing tri-n-octylphosphine oxide (TOPO) towards various anion forms of the strongly basic anion exchanger Dowex 1, X 8. In this procedure, the uranium is extracted from a 1N hydrochlorid acid solution containing ascorbic acid into diethyl ether and adsorbed from a mixture consisting of 50 vol.% ether (0.1N in TOPO), 45 vol.% methylglycol and5 vol.% 12N hydrochloric acid on the ion exchanger (chlorid form). Following elution with 1M hydrochloric acid, the uranium is determined either fluorimetrically or spectrophotometrically by the thiocyanate method. By means of this anion exchange procedure, it is possible above all to separate the uranium from all ions interfering with its fluorimetric or spectrophotometric determination and also from TOPO itself. In particular, consideration is given to the spectrophotometric determination of the uranium in the presence of larger amounts of molybdenum, and a method was worked out for the removal of this element.相似文献
77.
Starting from the binuclear complex [RhCl(NBD)]2 (NBD = 2,5-norbornadiene) in the presence of the phosphines L = PMe3, PMe2Ph, PMePh2, PEt3, PEt2Ph, PEtPh2, or P(n-butyl)3, various mononuclear dihydrides of the type Rh(H)2CIL3, i.e., those of the homogeneous hydrogenation catalysts RhCIL3, have been obtained upon addition of parahydrogen, and their 1H NMR spectra have been investigated using parahydrogen-induced polarization (PHIP). Furthermore, the two binuclear complexes (H)(Cl)Rh(PMe3)2(mu-Cl)(mu-H)Rh(PMe3) and (H)(Cl)Rh(PMe2Ph)2(mu-Cl)(mu-H)Rh(PMe2Ph) have been detected and characterized by means of this in situ NMR method. Analogous complexes with trifluoroacetate instead of chloride, i.e., Rh(H)2(CF3COO)L3, have been generated in situ starting from Rh(NBD)(acac) in the presence of trifluoroacetic acid in combination with the phosphines L = PPh3, PEt2Ph, PEt3, and P(n-butyl)3, and their 1H NMR parameters have been determined. 相似文献
78.
The complex [C5H5RhH(C2H4)PMe3]BF4 (I) reacts with NaF and NaCN by deprotonation to give C5H5Rh(PMe3)C2H4 but with NaCl, NaBr and NaI the ethylrhodium compounds C5H5RhC2H5(PMe3)X (II–IV) are obtained. The reactions of I with CO and PPri3 yield the BF4 salts of the cations [C5H5RhH(CO)PMe3]+ and [C5H5RhH(PPri3)PMe3]+ (V, VI), respectively, from which the uncharged complexes C5H5Rh(CO)PMe3 (VII) and C5H5Rh(PPRi3)PMe3 (VIII) are prepared. The carbonyl compound VII is also accessible either from C5H5Rh(CO)2 and PMe3 or from C5H5Rh(PMe3)2 and CO. The reaction of I with ethylene leads to the BF4 salt of the cation [C5H5RhC2H5(PMe3)C2H4]+ (X) which on treatment with PMe3 forms the complex [C5H5RhC2H5(PMe3)C2H4PMe3]BF4 (XI). The compound [C5H5RhH(C2H4)PPri3]BF4 (XII) reacts with NaI by insertion to yield C5H5RhC2H5(PPri3)I (XIII) whereas with PPri3 the salt [C5H5RhH(PPri3)2]BF4 (XIV) is produced. The bis(triisopropylphosphine) complex C5H5Rh(PPri3)2 (XVI) is obtained from XIV and NaH. 相似文献
79.
Anton Meller Walter Maringgele Rainer Oesterle 《Monatshefte für Chemie / Chemical Monthly》1980,111(5):1087-1096
The reaction of galliumtrichloride and galliumtribomide resp. with 2,6-dimethyl- and 2,4,6-trimethyl-N-trimethylsilyl-trifluoroacetanilide leads to the trifluoracetanilidodihalogenogallanes1–3. The 2,6,9-trioxa-4,8-diaza-1,5-digalla-bicyclo-[3.3.1]-nonadiene derivatives1 a–3 a are formed probably as by products.N-Trimethylsilyltrifluoroacetamide reacts with galliumtrichloride to yield the trifluoroacetamido-dichlorogallane4.N-Trimethylsilyl-N,N,N-triorganyl-thioureas react with galliumtrichloride under elimination of chlorotrimethylsilane to give the thio-ureido-gallanes5 and6. IfN,N-diorganylureas andN,N-diorganyl-thio-ureas resp. are reacted with galliumtrichloride and methyl-gallium-dichloride resp., the thio-ureido- and ureido-gallanes7–9 are obtained by elimination of hydrogenchloride. The compounds are characterized by analysis and spectral data (NMR:1H,19F; MS; IR). The substances are monomeric in the gas phase, obviously due to internal coordination.
30. Mitt.:W. Maringgele undA. Meller, J. Organomet. Chem., im Druck. 相似文献
80.
O. G. Koch 《Fresenius' Journal of Analytical Chemistry》1973,265(1):29-30
Zusammenfassung Zur Bestimmung von 2,5–100 ppm Sb in Eisen, unlegierten und niedrig legierten Stählen sowie in Automatenstählen wird das Antimon zuerst in 2 Stufen vorisoliert mit Hilfe der Spurenfällung mit Mangan(IV)-oxidhydrat als Spurenfänger und anschließender Jodidextraktion. Nach der Rückextraktion erfolgt die photometrische Bestimmung mit Methylfluoron in der wäßrigen Phase. Der relative Fehler beträgt ±5%, der Zeitbedarf für eine Einzelbestimmung 1,5 h.Herrn H. Sifirin danke ich für die sorgfältige Durchführung der Versuche. 相似文献