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991.
G. B. Golubitskii E. V. Budko E. M. Basova A. V. Kostarnoi V. M. Ivanov 《Journal of Analytical Chemistry》2007,62(2):152-156
The effects of acetonitrile and potassium dihydrogen phosphate concentrations in a mobile phase and the pH of the mobile phase on the retention of analgin (dipyrone) and anesthesin (benzocaine) on Symmetry C18 and Nova-Pak CN HP sorbents with grafted octadecylsilanol and nitrile groups, respectively, were studied. It was found that, under identical conditions, retention on the sorbent with grafted nitrile groups was weaker. A rapid and cost-effective procedure was developed for the determination of analgin and anesthesin in the analysis of Bellalgin tablets. 相似文献
992.
E. M. Peresleni M. Ya. Uritskaya V. A. Azimov V. A. Loginova T. F. Vlasova Yu. N. Sheinker L. N. Yakhontov 《Chemistry of Heterocyclic Compounds》1974,10(3):340-344
It was shown by means of IR, UV, and PMR spectra that -(3-nitro-2-pyridyl)pyruvic acid esters are practically completely enolized in the crystal state and in solution; ethyl -(3-nitro-4-pyridyl)pyruvate has an enol structure in the crystalline state and in pyridine solution but exists as a mixture of keto and enol forms in low-polarity solvents.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 389–393, March, 1974. 相似文献
993.
Formation of a nonequilibriuin gas-discharge plasma in air under the action of radiation at a wavelength of 10.6 with a duration of 10–6 sec is considered. It is shown that the air discharge occurs under nonequilibrium conditions by formation of an autoionization complex with subsequent oscillatory excitation of molecules. The molecular distribution function over oscillatory degrees of freedom is found in the diffusion approximation. The electron temperature and concentration in the breakdown plasma are calculated with consideration of multistep ionization of molecules and dissociative recombination of charged particles. Results are compared with experiment.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 9–13, February, 1985. 相似文献
994.
Harris RK Kinnear KA Morris GA Stchedroff MJ Samadi-Maybodi A Azizi N 《Chemical communications (Cambridge, England)》2001,(23):2422-2423
The first use of silicon-29 diffusion-ordered NMR spectroscopy (DOSY) is reported, in a study of the speciation of aqueous silicates. 相似文献
995.
R. A. Potyrailo S. E. Hobbs G. M. Hieftje 《Analytical and bioanalytical chemistry》1998,362(4):349-373
Current concepts for chemical and biochemical sensing based on detection with optical waveguides are reviewed. The goals are to provide a framework for classifying such sensors and to assist a designer in selecting the most suitable detection techniques and waveguide arrangements. Sensor designs are categorized on the basis of the five parameters that completely describe a light wave: its amplitude, wavelength, phase, polarization state and time-dependent waveform. In the fabrication of a successful sensor, the physical or chemical property of the determined species and the particular light wave parameter to detect it should be selected with care since they jointly dictate the sensitivity, stability, selectivity and accuracy of the eventual measurement. The principle of operation, the nature or the detected optical signal, instrumental requirements for practical applications, and associated problems are analyzed for each category of sensors. Two sorts of sensors are considered: those based on direct spectroscopic detection of the analyte, and those in which the analyte is determined indirectly through use of an analyte-sensitive reagent. Key areas of recent study, useful practical applications, and trends in future development of optical waveguide chemical and biochemical sensors are considered. 相似文献
996.
The current status, trends, and a specific role for macroligands in catalysis by heterogenized metallopolymeric complexes are considered. Relations between homogeneous catalysis, enzyme catalysis, and catalysis by heterogenized metal complexes are traced. The effects of various factors on the catalysis of the main reactions used in organic synthesis—hydrogenation, polymerization (in particular, under the action of immobilized metallocene and postmetallocene catalysts), and redox processes (such as the catalysis of oxygenation, hydroperoxide oxidation, epoxidation, and hydroformylation)—are analyzed. In this review, attention is focused on the nondestructive identification of intermediates and catalytically active species in heterogenized systems. Experimental evidence is presented in support of the fact that the high activity, stability, and selectivity of immobilized catalysts are associated with a dramatic inhibition of concerted reactions in the coordination sphere of a transition metal, which result in catalyst deactivation, as well as with substrate enrichment. Prospects for the development of these highly organized hybrid systems and possibilities to consider the main requirements imposed on metal complex catalysis even at the stage of designing them are predicted. 相似文献
997.
The reaction of carboxymethyl polysaccharides and their ethyl esters with amines was studied with the aim to determine how the structure of the polymeric acylating agent affects the composition of the reaction products. 相似文献
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