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961.
The capabilities of the electrophoretic separation of biogenic amines (adrenalin, noradrenalin, dopamine, serotonin, metanephrine, and normetanephrine) under conditions of capillary zone electrophoresis and micellar electrokinetic chromatography with the introduction of complex-forming agents (18-crown-6, 4,13-diaza-18-crown-6, and sodium dodecyl sulfate as an ion-pair reagent) and acetonitrile as the constituents of a working electrolyte were demonstrated. A technique for the sampling of biological fluids (urine, blood plasma, and serum) with the use of solid-phase extraction on aluminum oxide and a C18 reversed-phase sorbent was developed. The capabilities of various versions of the preconcentration of biogenic amines were determined, which allowed us to decrease the limits of detection by a factor of hundreds. 相似文献
962.
Pablo Rivera-Rodriguez Lena Ruiz-Ramirez Boris E. Zaitsev Tatiana M. Ivanova 《Transition Metal Chemistry》1986,11(12):447-448
Summary The Ru 3d5/2 and 3p3/2 x-ray photoelectron spectra of mono-and non-chlorinated ruthenium phthalocyanines were measured and the collected data on the core-level binding energies of ruthenium have been used to assess the oxidation state of the metal and the composition of the macrocyclic ligands. 相似文献
963.
The electrothermal atomization of the volatile elements arsenic, antimony and thallium from a refractory metal platform consisting of a tungsten coil and/or a refractory metal foil with the dimensions of a conventional graphite platform was studied. Several combinations of refractory metal platforms were investigated, as follows: W platform; Ta platform; W coil; W coil on a W platform and W coil on a Ta platform. The best combination for these elements as regards both thermal stabilization and sensitivity is the W coil on a Ta platform. Thermal stabilization is also achieved with a W coil on a W platform. The presence of Pd-containing chemical modifier favors the thermal stabilization of the analytes. The sufficient amount is 2 micrograms of Pd. The maximal temperatures of pyrolysis are higher (arsenic, antimony) or equal (thallium) to those when using different chemical modifiers, added as solutions. It may be concluded, that the refractory metal platforms act as "built-in modifiers". They are suitable for the determination of arsenic, antimony and thallium in samples of complex matrix composition where high thermal stability of the analytes during the pyrolysis step is required. 相似文献
964.
Fundamental aspects of film formation in electrochemical polishing of silver and silver-copper alloys in thiosulfate solutions 总被引:1,自引:0,他引:1
E. P. Grishina S. I. Galanin O. A. Ivanova 《Russian Journal of Applied Chemistry》2004,77(8):1283-1286
The anodic behavior of silver and its alloys with copper in thiosulfate solutions was studied by cycling voltammetry. A scheme of an electrochemical polishing process including the stage of formation of a resistive layer of silver thiosulfate and the chemical stage of its dissolution is suggested.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 8, 2004, pp. 1299–1302.Original Russian Text Copyright © 2004 by Grishina, Galanin, Ivanova. 相似文献
965.
V. V. Azatyan Z. S. Andrianova A. N. Ivanova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(7):1044-1049
The role of competition between reaction chain branching and termination at various burning stages accompanied by reaction mixture self-heating was studied by mathematically modeling combustion of hydrogen mixtures with air and oxygen at a 1 bar initial pressure. An algorithm was suggested that allowed chair branching to be switched off at various time moments during calculations with retaining all the other, including thermal, parameters. It was shown that the switching off of chain avalanches at any process stage resulted in virtually instantaneous burning termination no matter what level of reaction mixture self-heating was reached. 相似文献
966.
Lisichkina I. N. Ivanova A. G. Peregudov A. S. Belikov V. M. 《Russian Chemical Bulletin》2001,50(4):738-739
The peptide protons in N-acetyl-,-dehydrodipeptides (DHDP) dissociate in aqueous methanol in the presence of magnesium salts upon the addition of alkali, which favors the diastereoselectivities of their hydrogenation over Pd/C. By contrast, the N—H bonds of the N-acetyl groups in DHDP seem not to dissociate under these conditions. The dissociation of the peptide N—H bonds in strongly alkaline solutions was studied by 19F NMR spectroscopy for model compounds containing the 4-FC6H4 fragment. 相似文献
967.
968.
I. B. Borodina E. B. Pomakhina Ts. M. Ramishvili O. A. Ponomareva A. I. Rebrov I. I. Ivanova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(6):892-898
The alkylation of phenol with methanol on HY and CsY/CsOH catalysts was studied in situ under static conditions by 13C NMR spectroscopy. Attention was largely given to the identification of intermediate compounds and mechanisms of anisole, cresol, and xylenol formation. The mechanisms of phenol methylation were found to be different on acid and basic catalysts. The primary process on acid catalysts was the dehydration of methanol to dimethyl ether and methoxy groups. This resulted in the formation of anisole and dimethyl ether, the ratio between which depended on the reagent ratio, which was evidence of similar mechanisms of their formation. Subsequent reactions with phenol gave cresols and anisoles. Cresols formed at higher temperatures both in the direct alkylation of phenol and in the rearrangement of anisole. The main alkylation product on basic catalysts was anisole formed in the interaction of phenolate anions with methanol; no cresol formation was observed. The deactivation of acid catalysts was caused by the formation of condensed aromatic hydrocarbons that blocked zeolite pores. The deactivation of basic catalysts resulted from the condensation of phenol and formaldehyde with the formation of phenol-formaldehyde resins. 相似文献
969.
Ivanov E. V. Abrosimov V. K. Lebedeva E. Yu. Ivanova N. G. 《Russian Journal of General Chemistry》2003,73(5):665-674
The solubility of krypton in mixtures of H/D isotopomers of water (H2O, D2O) and methanol (CH3OH, CD3OH, CH3OD) was studied at 101325 Pa and 278.15-318.15 K with a 10 K step. The thermodynamic characteristics of Kr solvation were calculated. The densities of mixtures of water and methanol isotopomers at the examined temperatures were calculated with an error of no more than 1 × 10-
5 g cm-
3 in the entire composition range. Both in water and aqueous methanol, krypton behaves as a structure-making component, but the alcohol solvation surrounding of the Kr atoms is more labile and more susceptible to the breaking effect of temperature. 相似文献
970.
Quantitative Determination of Cationic and Nonionic Surfactants in Aqueous Solutions of Their Mixtures by Capillary Zone Electrophoresis 总被引:1,自引:0,他引:1
A method based on capillary zone electrophoresis is developed for a quantitative determination of cationic (dodecylpyridinium bromide) and nonionic (Triton X-100) surfactants absorbing in the UV region. The effect of the pH and ionic strength of the solution on the output time and shape of the resultant peaks is studied, and the optimal conditions of the analysis are determined. For both surfactants, the analytical signal (the area of the peak on the electrophoregram) is found to linearly depend on the concentration. It is established that the presence of a second surface-active component does not affect the signal of the surfactant analyzed; thus, surfactants may be quantitatively determined in both individual and mixed solutions. The method of capillary zone electrophoresis is shown to be applicable for determining the CMCs of surfactants. 相似文献