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981.
J. Knol A. Westerhof H.O. van Oven H.J. de Liefde Meijer 《Journal of organometallic chemistry》1975,96(2):257-258
The synthesis and some of the properties of the new complexes (h8-C8H8)-(h5-C5H5)TiI and (h8-C8H8)(h5-C5H5)TiI3 are described. 相似文献
982.
Y. BallesterosM.J. Gonzalez de la Huebra M.C. QuintanaP. Hernandez L. Hernandez 《Microchemical Journal》2003,74(2):193-202
The electrochemical behaviour of kinetin (6-furfurylaminopurine) on a carbon paste modified with OV-17 silicone electrode, is studied. The determination of kinetin is possible working in square wave voltammetric techniques, reaching limits of determination of 38.7 ng ml−1. The proposed method was successfully applied to determine the cytokinin in extracts of apples (previously spiked with kinetin) and the obtained results were in accordance with the results obtained with HPLC-UV. 相似文献
983.
Andrés Izquierdo Pilar Linares M. D. Luque de Castro Miguel Valcarcel 《Fresenius' Journal of Analytical Chemistry》1990,336(6):490-493
Summary Two fluorimetric methods are proposed for the simultaneous determination of ammonia and urea based on the reaction of the former with o-phthalaldehyde/2-mercaptoethanol and on the use of a dual injection system in which the valves are coupled in series or in parallel. An enzymatic reactor converts urea into ammonia which is determined by the same reaction. These configurations provide very similar results with a linear determination range between 0.5 and 10.0 g ml–1 and a sampling frequency of 60 h–1. The proposed methods are very tolerant to foreign species commonly found in water, as shown by applying them to samples of different origins. 相似文献
984.
M. Martín L. Sandoval J. F. Rivas-silva A. Palma 《International journal of quantum chemistry》1993,46(4):515-518
Squeezed states are normally studied in configuration space or using the Glauber formalism for the coherent states. Here we show that the use of the Fock–Bargmann space can lead to more general solutions, especially in the case of squeezed states associated with the square of field amplitude. The relations that we obtain are completely general and several well-known, approximate results can be obtained as the limit cases of our approach.© 1993 John Wiley & Sons, Inc. 相似文献
985.
de Magalhães Padilha P Rocha JC Moreira JC de Sousa Campos JT do Carmo Federici C 《Talanta》1997,45(2):317-323
Cellulose phosphate (CELLPHOS) was studied as a collector for analytical preconcentration of traces of Cd(II), Cr(III), Cu(II) and Ni(II) from aqueous sample solution. It has been proved that using chromatographic columns packed with CELLPHOS for preconcentration and 1.0 mol 1(-1) HCl for elution the adsorbed analytes are quantitatively enriched. An enrichment factor of 20 (100 ml sample, 5 ml concentrate) was achieved by this separation procedure, which was applied to a series of water analyses (river, sea, bog water). 相似文献
986.
Oxidation of alkynyl ethers and -amines with iodosylbenzene in presence of Ru-catalysts affords α-keto esters and α-keto amides in 44–85% yield. These conversions can also be effected with RuO4. 相似文献
987.
Hu D Croutxé-Barghorn C Feuillade M Carré C 《The journal of physical chemistry. B》2005,109(32):15214-15220
Hybrid sol-gel materials have been prepared by hydrolytic polycondensation of an alkoxysilane. The sol-gel process of methacryloxypropyltrimethoxysilane (MAPTMS) has been followed by fluorescence spectroscopy with 2-naphthol as a probe. The experimental results showed that this photoprobe was dramatically sensitive to the microenvironment polarity. Spectroscopic studies revealed fluctuations of the maximum emission intensity and wavelength as a function of time. These fluctuations were attributed to the amphiphilic behavior of the hydrolyzed precursor. The maximum emission wavelength of the probe corresponding to its protonated form was higher than in pure water. All the results suggest that the presence of water molecules, tightly bonded to the polar head of the silanols, increased locally the sol polarity and induced a red-shifted emission. Fluorescence spectroscopy emphasized the reversibility of monomeric silanol aggregates and the changes in hydroxy group number of the silica network during the sol maturation. The behavior of this system upon shaking confirmed this statement. 相似文献
988.
Multicomponent adsorption data of a fermentation broth containing adipoyl-7-amino-3-deacetoxycephalosporanic acid (adipoyl-7-ADCA), a cephalosporin precursor for 7-ADCA, and two key impurities, alpha-hydroxyadipoyl-7-ADCA and alpha-aminoadipoyl-7-ADCA were obtained from batch equilibrium and frontal chromatography tests. Amberlite XAD-1600 was chosen as the resin. A rate model was applied to simulate the chromatograms. An alkaline buffer, which by itself has no affinity for the resin, was used as the eluent. The widely used reversed-phase modulator model is inaccurate in explaining the stepwise elution data. A new model, the induced competition model, has been developed to account for apparent retention of the buffer in the presence of adsorbed species. Close agreement between the simulations and the data was achieved with the new model. 相似文献
989.
van Dongen BE Schouten S Damsté JS 《Rapid communications in mass spectrometry : RCM》2001,15(7):496-500
Monosaccharides were derivatized using methylboronic acid and N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA), and the delta13C values of these derivatives measured by gas chromatography/combustion/isotope-ratio-monitoring mass spectrometry to determine the original 13C-content of the monosaccharides. Comparison with the measured off-line delta13 values of the monosaccharides shows that no fractionation in 13C takes place during derivatization. The methylboronic derivatization method has proven to be a new method for natural abundance isotopic analysis of intact monosaccharides (arabinose, xylose, fucose, fructose and glucose). The method is rapid, does not involve isotopic fractionation during derivatization, and gives more precise delta13C values than other methods reported. The method was successfully applied to determine the delta13C value of glucose of the freshwater alga Scenedesmus communis. 相似文献
990.
Jayaraman Chandrasekhar Eluvathingal D. Jemmis Paul von Ragué Schleyer 《Tetrahedron letters》1979,20(39):3707-3710
The 3,5-dehydrophenyl cation (I), which may represent the structure of C6H3 ions observed mass spectroscopically, illustrates : two different aromatic systems in orthogonal planes. 相似文献