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961.
The kinetics of streptomycin degradation by hydrogen peroxide at pH 7.4 was investigated. The reaction was catalyzed by traces of Cu(II) ions, and it was followed spectrophotometrically at 322 nm by applying the initial-rate method. The kinetic parameters of the reaction are reported, and a rate equation is suggested. From the dependence of the relative rate constants on the temperature, the activation energy was calculated to be 57.5 kJ/mol. Based on this reaction, a kinetic method for streptomycin determination is proposed. The calibration graph is linear in the ranges 1.94 - 15.48 microg/cm(3) and 0.15 - 1.94 microg/cm(3). The influence of foreign ions and molecules on the accuracy of the determinations was investigated. The proposed kinetic method has high selectivity and good sensitivity, and enabled to determine streptomycin in pharmaceutical samples. 相似文献
962.
Olga Ordeig Craig E Banks Trevor J Davies F Javier del Campo Francesc Xavier Mu?oz Richard G Compton 《Analytical sciences》2006,22(5):679-683
Gold ultra-microelectrode arrays are used to explore the electrochemical oxidation of hydroxide ions and are shown to be analytical useful. Two types of ultra-microelectrode arrays are used; the first consist of 256 individual electrodes of 5 microm in radius, 170 of which are electrochemically active in a cubic arrangement which are separated from their nearest neighbour by a distance of 100 microm. The second array compromises 2597 electrodes of 2.5 microm in radius and of which 1550 of which are electrochemically active in a hexagonal arrangement separated by the nearest neighbour by 55 microm. Well defined voltammetric waves are found with peak currents proportional to the concentration of hydroxide ions in the range 50 microM to 1 mM. Detection limits of 20 microM using the 170 ultra-microelectrode and 10 microM with the 1550 ultra-microelectrode array are shown to be possible but with a higher sensitivity of 4 mA M(-1) observed using the 1550 ultra-microelectrode array compared to 1.2 mA M(-1) with the 170 ultra-microelectrode array. 相似文献
963.
Synthesis and characterization of ciprofloxacin compounds with cadmium(II) and mercury(II) chlorides
N. N. Golovenv S. D. Kirik I. I. Goloveneva M. E. Nishnevich 《Russian Journal of Inorganic Chemistry》2006,51(3):415-420
Five new compounds of ciprofloxacin (CfH = C17H18FN3O3) with cadmium(II) and mercury(II) chlorides were synthesized. The compounds were characterized by chemical analysis, powder X-ray diffraction, pH-metric titration, UV spectroscopy, and thermal analysis. 相似文献
964.
L. V. Miroshnik N. I. Korovnikova Yu. V. Shabadash 《Russian Journal of Inorganic Chemistry》2006,51(4):649-655
The complexing properties of cellulose complexite with respect to copper(II) ions in water-1,4-dioxane (DO) mixtures are determined. The stoichiometry and stability constants of copper(II) complexes with the hydroxamic groups of the polymer are determined. The equilibrium speciation diagrams for the complexes at pH 2.0–6.0 are plotted; stereochemical configurations are suggested. The effect of the solvation parameters of the complexite on complex formation is analyzed. 相似文献
965.
V. M. Novotortsev S. A. Varnavskii S. F. Marenkin L. I. Koroleva R. V. Demin V. M. Trukhan S. O. Klimonskii V. D. Kuznetsov 《Russian Journal of Inorganic Chemistry》2006,51(8):1153-1156
Solid solutions Cd1?x MnxGeP2 (x=0?0.19) have been synthesized and identified. In these solutions, the unit cell parameters decrease with an increase in the manganese content. The solid solution Cd0.81Mn0.19GeP2 is a ferromagnet with the Curie temperature T C ≈ 311 K. The paramagnetic moment of Mn2+ ions equal to 5.8 μB, as well as the spontaneous magnetization constituting 76% of the total magnetization of a crystal, has been determined with the use of the Langevin function. The origin of ferromagnetism in CdGeP2:Mn is exchange mediated by charge carriers (holes). These holes are caused by cationic defects in the structure of chalcopyrite. 相似文献
966.
G. M. Mamardashvili R. S. Kumeev N. Zh. Mamardashvili 《Russian Journal of Inorganic Chemistry》2006,51(8):1264-1269
The formation of host-guest complexes between dimeric cyclophane zinc diphenylporphyrinates and bidentate ligands of different nature containing two nitrogen atoms has been studied by the spectrophotometric titration method and 1H NMR spectroscopy in a toluene-methanol (2: 1) binary solvent. The complexation of these dimeric porphyrinates with 1,4-diazabicyclo[2,2,2]octane or pyrazine can lead to 1: 1 or 1: 2 complexes, depending on the metalloporphyrin-to-ligand molar ratio. The stability constants of the porphyrinate-ligand complexes and concentration ranges of their formation have been determined. 相似文献
967.
968.
In the present work, the general method proposed earlier for calculating the distribution density and moments of the absorbed energy in isolated sensitive regions of absorbers irradiated by ionizing particles is developed and made specific for the electron-photon problem. Electron transfer is considered within the framework of a model using grouping of excitations and slipping ionization; the presence of electron equilibrium in the vicinity of sensitive regions is assumed. Two similar methods of calculating these characteristics are developed. Both reduce the initial problem to two independent problems: determining the electron spectrum in the sensitive region (in one of the methods, the spectrum of electron sources is also needed) and calculating the coefficients characterizing electron transfer in the sensitive region and its immediate vicinity.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 89–94, September. 相似文献
969.
S. Ebel B. Reyer und A. Werner-Busse 《Fresenius' Journal of Analytical Chemistry》1987,327(2):193-197
Summary This paper describes a reliable working station for the in line-process control in chemical plants. Essential parts of the equipment (pump, column) are in duplicates and may be combined by computer control in different lines. One pump and column is in working position, the other is held in ready to work position by conditioning. While one column is in working position, the system is able to calibrate the other column and to switch to this column in the case of breakdown of the other column. By means of chromatographic data (as retention time, peak height of standards, data of separation) the working column is under control and the switching to the other column is down before a real breakdown. The status of the detector is followed by number and distance in time of the necessary auto-zero operations and by the noise of the lamp.
Herrn Prof. Dr. W. Fresenius aus Anlaß des 125jährigen Erscheinens der Fresenius Zeitschrift für Analytische Chemie gewidmet 相似文献
Herrn Prof. Dr. W. Fresenius aus Anlaß des 125jährigen Erscheinens der Fresenius Zeitschrift für Analytische Chemie gewidmet 相似文献
970.
Complex dielectric spectroscopy (frequency range 5 Hz-13 MHz) has been used to analyse the frequency, temperature and bias-field dependences of the molecular dynamics of a very high-spontaneous-polarization ferroelectric liquid crystalline material exhibiting SmA, SmC* and unknown SmX smectic phases. Different smectic phase transition temperatures have been observed from the study of the temperature dependence of the dielectric strength and the relaxation frequency. The phase transition temperatures (crystalline to isotropic phases) have also been described very accurately from the temperature-dependent symmetric and asymmetric shape parameters of the relaxation function and also the dc conductivity. In a planar aligned cell, two symmetric modes (Goldstone mode and domain mode) have been observed in both the SmX and SmC* phases. One asymmetric mode (X-mode) observed in the SmC* and SmA phases could be related to the interaction of dipoles of the ferroelectric liquid crystals being affected by the surface of the cell. The soft mode, which usually appears very close to the SmC*-SmA phase transition was not observed until the bias field was applied. The second order nature of the SmC*-SmA phase transition was revealed. 相似文献