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991.
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
992.
A simple field sampling-preconcentration method for zinc determination in seawater is described. Seawater was collected in situ by pumping it through a minicolumn packed with a chelating resin (Chelite P) connected to a field flow preconcentration system (FFPS). These packed minicolumns retain the dissolved zinc, and once are loaded with the analyte, they are returned to the laboratory where they are sequentially inserted into a flow injection system for on-line zinc elution with diluted hydrochloric acid and flame atomic absorption spectrometric detection. A factorial design has been used to optimize the FFPS and the flow injection elution process. The proposed method has a linear calibration range from 0.07 to at least 9.4 microg L(-1) of zinc, with a detection limit of 0.02 microg L(-1) and a throughput of 26 samples h(-1). Validation was carried out against certified reference water samples. This procedure has been successfully applied to the determination of Zn in seawater samples from Galicia (Spain). 相似文献
993.
Solid-phase extraction (SPE) is an effective tool for the preconcentration of trace elements and their separation from various sample constituents. Octadecyl and other alkyl-bonded silica gels are most widely used for these purposes. The fundamentals of the SPE of inorganic ions are reviewed and compared with those of related techniques (liquid-liquid extraction and reversed-phase liquid chromatography). The extraction of ions in the form of chelate compounds, inorganic salts solvated by neutral reagents, and ion-pair compounds is considered. Numerous applications of SPE to the separation and preconcentration of different elements and their species, including on-line combinations with instrumental determination techniques, are described and tabulated. 相似文献
994.
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
995.
M. R. Khairulaev D. Kh. Dadaev M. M. Rasulov 《Russian Journal of Inorganic Chemistry》2006,51(11):1706-1709
Contact melting (CM) in the lead-tellurium system is considered. Spontaneous temperature elevation is observed as a result of the exothermic reaction of lead telluride formation in the contact site. The effects of direct current (dc) and dopants on the CM temperature are studied. 相似文献
996.
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
997.
M. B. Babanly G. M. Guseinov D. M. Babanly F. M. Sadygov 《Russian Journal of Inorganic Chemistry》2006,51(5):810-813
The polythermal sections TlBr-Tl2S, TlBr-Tl4S3, TlBr-TlS, and Tl6SBr4-Tl; the isothermal section at 300 K of the phase diagram; and the projection of the liquidus surface of the Tl-S-Br system have been investigated in the composition region Tl-TlBr-S by DTA, X-ray powder diffraction analysis, and microhardness measurements. The primary crystallization regions, including that of the only ternary compound (Tl6SBr4), have been determined, and the types and coordinates of the invariant and univariant equilibria in the phase diagram are determined. 相似文献
998.
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
999.
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
1000.