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151.
The reactivity of the fluorescent reagent calcein with the trivalent cations of the rare earths has been spectrofluorimetrically studied in aqueous solution. Optimum excitation and emission wavelengths were 492-497 and 519-522 nm, respectively. Optimum pH was in the range 6.0-9.2. The stoichiometry of the complexes was 1:1. A direct, rapid and sensitive method for the determination of rare earth mixtures has been proposed with a detection limit of 4.49x10(-8) M and a coefficient of variation of 0.82%. 相似文献
152.
Poly-(butanediol-1,4-adipate) and poly-(diethyleneglycol-succinate) polyesters and their ionized derivatives, containing Mg2+ and Zn2+ ions with different stoichiometric ratios to the chain-end COOH groups of the polyesters have been investigated by derivatograph.The thermal decompositions of the metal-containing polyesters differ significantly from those of the unionized polyesters. These differences are connected with the chemical repeating unit of the polyesters and the chemical nature of the metal ions, and proportional to the amount of the latter.An explanation is given of the catalytic effect of metal ions on the process of decomposition of the polyesters.
Zusammenfassung Poly-(butandiol-1,4-adipat) und Poly-(diethylenglycolsuccinat) polyester und ihre «ionisierten» Derivate — mit Mg2+ — und Zn2+-Ionengehalt in verschiedenen stöchiometrischen Verhältnissen zu den endständigen COOH-Gruppen der Polyester — wurden im Derivatographen untersucht.Die thermische Zersetzung der metallhaltigen Polyester unterscheidet sich wesentlich von nicht-ionisierten Polyestern. Diese Unterschiede sind mit den sich wiederholenden chemischen Einheiten der Polyester und der chemischen Beschaffenheit der Metallionen verbunden, und proportional dem Anteil derselben.Es wird eine Erklärung des katalytischen Effekts der Metallionen auf den Zersetzungsvorgang der Polyester gegeben.
-1,4 «» , Mg2+ Zn2+ . , «» . . .相似文献
153.
Varga I Mészáros R Szakács Z Gilányi T 《Langmuir : the ACS journal of surfaces and colloids》2005,21(14):6154-6156
A simple one-step synthesis is described for the functionalization of poly(vinyl chloride) used for the preparation of anionic surfactant-selective membrane electrodes. The method is based on the nucleophilic substitution of a fraction of the chlorine atoms bound to the poly(vinyl chloride) backbone by trimethylamine. The prepared slightly charged polymer gave rise to high-quality surfactant-selective electrode membranes, which had a Nernstian response, short response time, and appropriate stability. 相似文献
154.
The stereochemistry of the cyclodehydration of (±)- and meso-2,5-hexanediol on the action of various dehydrating agents was investigated. The earlier assumed and confirmed intramolecular SN2 mechanism for acid-catalysed ring-closure was found to hold in most cases. Various extents of racemisation can be observed on the action of certain Lewis acids, and the solvents concentrated H2SO4 and HMPT (hexamethyl phosporic acid triamide) under previously unexamined reaction conditions. 相似文献
155.
Lázló Markó 《Journal of organometallic chemistry》1981,213(1):271-275
Two new mixed iron cobalt carbonyl sulphide clusters HFe2(CO)9S and Fe2Co(CO)8(NO)S have been prepared and characterized. The hydride complex undergoes acidic dissociation in polar solvents and the resulting anion was isolated as (Et4N)[Fe2Co(CO)9S]. An efficient high pressure synthesis has been found for H2Fe3(CO)9S. 相似文献
156.
Summary The sensitivity of colorimetric determinations based on reduction of extinction by complex-forming anions can be increased by measuring the change of absorbancy in the organic phase after shaking with a suitable solvent, i. e. by determining the interference of the anion with extractability. This principle has been applied to the determination of the fluoride ion.
Zusammenfassung Die Empfindlichkeit kolorimetrischer Bestimmungen, die auf Herabsetzung der Extinktion durch komplexbildende Anionen beruhen, kann durch Messung der Absorptionsänderung in der organischen Phase nach Schütteln mit einem geeigneten Lösungsmittel, das heißt durch Bestimmung der durch das Anion verminderten Extrahierbarkeit, erhöht werden. Dieses Prinzip wurde auf die Bestimmung von Fluoridion angewendet.
Résumé La sensibilité des déterminations colorimétriques basée sur l'effet de diminution d'extinction dû à des anions donnant lieu à la formation de complexes peut être accrue par la variation de l'absorption dans la phase organique après agitation avec un solvant approprié, ce qui revient à déterminer l'effet d'empêchement d'extraction dû à l'anion. Ce principe a été appliqué au dosage de l'ion fluorure.相似文献
157.
D. Batsurén É. Kh. Batirov V. M. Malikov M. R. Yagudaev 《Chemistry of Natural Compounds》1983,19(2):134-138
From the roots and epigeal parts ofHaplophyllum dauricum (L.) G. Don., new acylated courmarin glycosides have been isolated: dauroside A, C23H28O13, mp 145–147°C (ethanol), []
D
22
– 72.7° (methanol), and dauroside B, C30H32O14, mp 145–150°C (methanol) []
D
22
0° (pyridine). Their structures have been established on the basis of chemical transformations and IR, UV, mass,1H NMR and13C NMR spectra.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 142–147, March–April, 1983. 相似文献
158.
J. Kristóf J. Inczédy J. Paulik F. Paulik 《Journal of Thermal Analysis and Calorimetry》1979,15(1):151-157
A technique developed for the continuous and selective detection of water vapour formed during thermal decomposition reactions is described. The device can be connected to different types of thermoanalytical instruments without any difficulties. The detector can closely follow changes in the amount of water released during decomposition reactions, with negligible time delay. The signal curves obtained by the detector can be compared to the simultaneously recorded thermoanalytical curves and used to determine the step in which the water was released. The device as a free standing unit can be used to detect water plugs in different gas flows as well. 相似文献
159.
The flavonoid composition of broccoli inflorescences has been studied by LC/UV-DAD/ESI-MSn. A large number of hydroxycinnamic acid esters of kaempferol and quercetin glucosides has been characterised. The structures of the flavonoid glycosides were analysed after alkaline hydrolysis, and were identified as 3-sophoroside/sophorotrioside-7-glucoside/sophoroside of kaempferol, quercetin and isorhamnetin (this last found in trace amount). These complex quercetin and isorhamnetin glucosides have not been previously characterised in nature. In addition, several less complex glucosides based on the same aglycones have been identified. The effect of sugar substitution and acylation on chromatographic mobility and ESI ionisation and fragmentation are discussed. 相似文献
160.