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991.
The sulphide-selective electrode is applicable to the determination of dithiooxamide by titration with silver nitrate. The effect of the alkali content of the solutions on the reaction has been studied. The reaction products are silver sulphide, oxalic acid, and nitric acid. If the alkali concentration of the solution is lower than that equivalent to the acid formed during the titration, the amount of sulphide produced by hydrolysis decreases and the equilibrium potential is established more slowly.The determination is rapid and accurate in the presence of 1 M sodium hydroxide. 相似文献
992.
Albert Lévai Gábor Tóth Áron Szőllősy Tibor Timár 《Monatshefte für Chemie / Chemical Monthly》1990,121(5):403-411
Summary Arylsulfonyloxy-2,2-dimethyl-2H-chromenes (26–35) have been synthesized by reduction of arylsulfonyloxy-2,2-dimethyl-4-chromanones (6–15) followed by dehydration.
Synthese von Benzopyranderviaten. 15. Mitt.: Darstellung von Arylsulfonyloxy-2,2-dimethyl-2H-chromenen
Zusammenfassung Reduktion von Arylsulfonyloxy-2,2-dimethyl-4-chromanonen (6–15) und anschließende Dehydratisierung liefert Arylsulfonyloxy-2,2-dimethyl-2H-chromene (26–35).相似文献
993.
J. Šňupárek L. Mrkvičková O. Quadrat Z. Walterová P. Bradna 《Colloid and polymer science》2000,278(12):1205-1210
Model ethyl acrylate–methacrylic acid copolymer latices and latices of particles cross-linked by copolymerizing small amounts
of water-soluble N,N′-methylenebisacrylamide were prepared by nonseeded semicontinuous emulsion copolymerization. Dynamic and static light scattering
measurements indicated a slightly higher degree of polydispersity in the case of cross-linked particles, especially in the
initial stages of polymerization. The hydrodynamic volume of the alkalinized particles controlling the viscosity properties
of the dispersions decreased with the time of polymerization and in the case of cross-linked copolymer almost reached a constant
value at about 1 h. The different character of the particle structure was confirmed by differences in particle disintegration
after alkali addition or in the presence of methanol.
Received: 2 February 1999/Accepted: 28 June 2000 相似文献
994.
Kubíček Vladimír Kučová Daria Císarř Prřemysl Burešová Vlasta 《Mikrochimica acta》2003,142(4):273-276
An ion-pair extraction spectrophotometry method was developed for the determination of fenpiverine bromide in tablets. To determine this substance it was necessary to find experimental conditions that would allow eliminating the influence of other components of the tablets. Attention was paid to the fact that a suitable pH of water phase was necessary to achieve high selectivity.Received December 11, 2002; accepted April 24, 2003
Published online July 28, 2003 相似文献
995.
Fluorimetric and UV methods of detection for liquid chromatographic determination of phenothiazines (chlorpromazine, acetopromazine and propionylpromazine) were developed. The effects of several experimental parameters on the separation and the sensitivity of the methods were evaluated. The detection limits ranged from 31 to 350 ng ml−1. Optimized methods were successfully applied to determination of the promazines in bovine liver samples. 相似文献
996.
[reaction: see text] A new route to oxcarbazepine (Trileptal), the most widely prescribed antiepileptic drug, starting from commercially available 2'-aminoacetophenone and 1,2-dibromobenzene, is reported. The sequentially accomplished key steps are palladium-catalyzed intermolecular alpha-arylation of ketone enolates and intramolecular N-arylation reactions. After several experiments to establish the best conditions for both arylation processes, the target oxcarbazepine is obtained in a satisfactory overall yield, minimizing the number of steps and employing scalable catalytic procedures developed in partially aqueous media. 相似文献
997.
The optical characteristics of absorption and circular dichroism (CD) spectroscopy of an alpha-subunit of C-phycocyanin (C-PC) were investigated by using time dependent density functional theory (TDDFT) combined with the polarizable continuum model (PCM). When the protonation of alpha-84 phycocyanobilin (PCB) and its interaction with the protein moiety in C-PC have been taken into account, satisfactory assignment of the absorption and CD spectra of alpha-84 PCB can be achieved. The TDDFT-PCM calculations conclude that in the visible absorption region the main peak arises from the pi electron excitation of the pyrrole rings and the shoulder peak comes from the charge transfer from Asp87 (a nearby amino acid residue) to PCBH(+). 相似文献
998.
Ruiz-Medina A Ortega-Barrales P Fernández-de Córdova ML Molina-Díaz A 《Journal of AOAC International》2002,85(2):369-374
A simple, rapid, inexpensive, and automated flow-through solid-phase spectroscopic sensing device is proposed for the sequential determination of 2 vitamins: thiamine and ascorbic acid. The vitamins are concentrated on ion-exchange gels, thiamine on Sephadex SP C-25, and ascorbic acid on Sephadex QAE A-25; both solid supports are packed in 2 different flow cells. The absorbance is monitored directly on the solid phase with a double-beam spectrophotometer at 250 nm, without derivatization or additional elution. With the use of 2 carrier/self-eluting solutions (0.1 5M sodium acetate/acetic acid and 0.18M citric acid/K2HPO4) and a sample volume of 1000 microL, the sensor responds linearly in the range of 0.5-15 and 3-50 microg/mL with detection limits of 0.14 and 0.36 microg/mL for thiamine and ascorbic acid, respectively. When the method was applied to synthetic samples and pharmaceutical preparations, precise and accurate values were obtained. 相似文献
999.
巯基化合物的电位分析法研究 总被引:3,自引:0,他引:3
本文对用直接电位法测试巯基化合物的可行性进行了研究。发现由硫化银,硫化汞等金属难溶盐制成的膜电极对6-巯基嘌呤,高胱氨酸,1,4-二巯基苏糖经合物可产生响应,其斜率为30-110mV/pC,电极响应时间,则为十几秒至十几分钏,测试结果具有较好的重现性。因此,该方法可望得到应用。文中还对有关响应机理进行了探讨。 相似文献
1000.
Gy. Marosi R. Lágner Gy. Bertalan P. Anna A. Tohl 《Journal of Thermal Analysis and Calorimetry》1996,47(4):1155-1161
Nucleating and transcrystallization behaviour of additives in engineering PP composites and the effect of modified interfacial structure is the subject of this series of papers. The first part concentrates on polypropylene/liquid crystalline polyester blends. Increased crystallisation temperature and degree of crystallinity of polypropylene is characteristic to the blends containing different amount of LCP additive. Transcrystallization process governs the formation of crystalline structure in these systems in course of isothermal crystallisation at 132C. The nucleating effect of LCP gives rise to more uniform crystalline structure in the polypropylene phase.The financial support of the OTKA 014194 is acknowledged with gratitude. 相似文献