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991.
Xie Z Sielemann S Schmidt H Li F Baumbach JI 《Analytical and bioanalytical chemistry》2002,372(5-6):606-610
A combination of a custom-designed ion mobility spectrometer (IMS) with a UV ionization source and a high speed capillary column (HSCC) has been developed as an analytical device for the sensitive detection of volatile organic compounds (VOCs), e.g. 2-propanone (acetone), 2-butanone and 3-pentanone (diethyl ketone) in the gas phase. A fast separation of the three selected substances and benzene, toluene and m-xylene (BTX) - all of which occur in human breath - has been achieved within less than four minutes at a carrier gas flow rate of 4.5 mL x min(-1). Multi-dimensional correlations presented support the interpretation of the acquired spectra of mixtures. Method detection limits were 2.7 microg x L(-1) for acetone and 2-butanone and 3.0 microg x L(-1) for diethyl ketone in nitrogen, respectively. The assay linear dynamic range is 4-320 microg x L(-1). 相似文献
992.
A novel 18,19-seco-ursane saponin, aculeoside I (1), in addition to four known saponins were isolated from the leaves of Ilex aculeolata Nakai and identified by using spectroscopic and chemical methods. The structure of the new saponin was established as 3,19-dihydroxyl-16,21-epoxy-18,19-seco-13(18)-urs-ene-28-oic-acid-19-O-alpha-L-rhamnopyranosyl-(1 --> 2)-alpha-L-arabinopyranoside. 相似文献
993.
ULTRASONICALLY DISPERSED POTASSIUM AS DEPROTONATING AND COUPLING AGENT──SYNTHESIS OF 1,6-DINITRILES IN SITUULTRASONICALLYDISP... 相似文献
994.
995.
钪—铋—三溴偶氮胂混合多核络合物显色反应及其在钪光度分析中应用研究 总被引:3,自引:0,他引:3
本文研究了钪-铋-三溴偶氮胂络合物的共显色反应。实验表明,共显色反应是由于形成混合多核络合物所致。钪络合物最大吸收峰在635nm,表观摩尔吸光系数为7.1×10~4L·mol~(-1)·cm~(-1)。钪在0~5μg/25ml遵守比尔定律。 相似文献
996.
本文研究了2-(-5-Br-2吡啶偶氮-5-二乙氨基)-酚与铑(Ⅲ)的显色反应。在pH为4.0的邻苯二甲酸氢钾缓冲液介质中,Rh(Ⅲ)与试剂形成稳定的橙红色络合物,其组成比为1:4,最大吸收波长为490nm,表现摩尔吸光系数为1.3×10 ̄5L·mol ̄(-1)·cm ̄(-1)。铑含量在0~4μg/10mL范围内服从比尔定律。 相似文献
997.
Hong-wu Xu Lin Pin Jin-xia Li Zhong-ning Chen Ji-gui Wu 《Transition Metal Chemistry》2007,32(6):781-783
A novel heterohexanuclear complex [Ni2Ag4(μ-dppm)4(pymt)6](SbF 6)2 · 2DMF · H2O (1), was synthesized by self-assembly with [Ag2(μ-dppm)2(MeCN)2](SbF6) 2 and [Et4N][Ni(pymt)3] (dppm = bis(diphenylphosphino)methane, pymt = pyrimidine-2-thiolate) as components and characterized by IR spectra, elemental analysis,
1H-NMR spectrum, 31P-NMR spectrum and Visible-Ultraviolet spectrum. Structure of the complex was determined by X-ray analysis. 相似文献
998.
Ford RC Ruffle SV Ramirez-Cuesta AJ Michalarias I Beta I Miller A Li J 《Journal of the American Chemical Society》2004,126(14):4682-4688
We have previously used inelastic incoherent neutron scattering spectroscopy to investigate the properties of aqueous suspensions of biomolecules as a function of hydration. These experiments led to the identification of signals corresponding to interfacial (hydration) water at low water content. A prediction from these studies was that in the crowded environment inside living cells, a significant proportion of the water would be interfacial, with profound implications for biological function. Here we describe the first inelastic incoherent neutron scattering spectroscopy studies of living cells and tissues. We find that the interfacial water signal is similar to that observed for water interacting with purified biomolecules and other solutes, i.e., it is strongly perturbed in the librational and translational intermolecular optical regions of the spectrum at 20-150 meV. The ratio of interfacial water compared to total water in cells (approximately 30%) is in line with previous experimental data for hydration water and calculations based on simple assumptions. 相似文献
999.
The combination of Lewis and Bronsted acids catalyzed the addition of beta-ketoesters to cyclic diene. Lactonization occurs in situ to afford fused bicyclic lactones directly. The catalysis provides an expedient route to bicylic lactones via a zip-process. 相似文献
1000.
A series of N-aryl β-bromodifluoromethyl β-enaminoketones were regioselectively synthesized in good yield by the reaction of N-aryl bromodifluoroacetimidoyl chlorides with methyl ketones. β-Bromodifluoromethyl β-enaminoketones smoothly cyclized to give a novel class of cyclic (2,2-difluoro-5-phenyl-furan-3-ylidene)-aryl-amines under basic condition. An intramolecular halophilic substitution mechanism was proposed. 相似文献