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1.
Sadao Takagi Mune Maeda 《Journal of inclusion phenomena and macrocyclic chemistry》1984,2(3-4):775-780
The enthalpies of transfer of cyclohexanol from aqueous to aqueous - or -cyclodextrin solutions have been measured at various mole fractions at 298.15 K on a rocking twin-microcalorimeter of heat-conduction type and the molar enthalpies, Gibbs energies, and entropies of inclusion in the aqueous solutions have been determined by the method proposed by the authors [Netsu Sokutei
10, 103 (1983)], to elucidate the driving force of the molecular inclusion. Discussions are given for all the systems obtained by the authors, concluding that the driving force is the enhancement of the entropy.Calorimetric studies on molecular inclusion V. 相似文献
2.
A new method of SS-RTP for the determination of trace silver has been established. This method is based on the fact that Ag+, when activated by ,-bipyridyl (bipy) in a media of HAc–NaAc (pH=4.9), can catalyze the reaction of Rhodamine B (RhoB) oxidized by K2S2O8, thus causing the Solid Substrate Room-Temperature Phosphorescence (SS-RTP) of RhoB to be quenched. The activating efficiency of bipy is 6.7 times higher than that of o-phenanthroline (phen). The reduction of the phosphorescence intensity (Ip) of RhoB is directly proportional to the concentration of Ag+ ions in the range of 1.6016.0agspot–1 (0.40µLspot–1). The regression equation of the working curve can be expressed as Ip=18.78+5.100mAg+ (agspot–1) (r=0.9994, n=6), the detection limit is 0.28agspot–1. This rapid, accurate and sensitive method has been successfully applied to the determination of trace silver in tea and human hair samples, and the results agree well with the Atomic Absorption Spectroscopy (AAS) method. The mechanism of the catalyzing reaction is also discussed. 相似文献
3.
Shu -Chuan Liang You -Lan Zhong und Zhi Wang 《Fresenius' Journal of Analytical Chemistry》1984,318(1):19-21
Zusammenfassung In dieser Arbeit werden Untersuchungsergebnisse über die Anreicherung von Spuren Scandium (0,4 bis 40 ppb) aus wäßriger Lösung mittels Schaumflotation mitgeteilt. Mit Hilfe von Eisen(III)hydroxyd (als Spurenfänger), einem Tensid und einem Stickstoffstrom werden die Spuren im Schaum eingefangen. Nach Abtrennung von der wäßrigen Lösung wird der Scandiumgehalt im Schaum entweder spektralphotometrisch mit Arsenazo III oder durch elektrothermische AAS ermittelt. Optimale Werte wurden ausgearbeitet für die notwendige Menge Tensid (Natriumoleat oder Cetyltrimethylammoniumbromid, CTAB) zur optimalen Anreicherung, für den pH-Bereich der Flotation und zum Erreichen einer Genauigkeit von 0,40 g Scandium aus 500-ml-Lösung bei der folgenden Bestimmung durch elektrothermische AAS. Natriumoleat ist für die Anreicherung von Scandium besser geeignet als CTAB.
Dedicated to Prof. Dr. W. Fresenius on the occasion of his 70th birthday
Presented at the China-Japan Bilateral Conference on Analytical Chemistry, Changchun, China, Sept. 14–17th, 1983 相似文献
Enrichment of traces of scandium from aqueous solutions by means of flotation
Summary This paper reports some experimental results of the enrichment of trace of scandium (0.4 to 40 ppb) from aqueous solutions by means of the adsorptive bubble (or adsubble) technique. With ferric hydroxide (as trace gatherer), a surfactant and a nitrogen stream, traces of scandium can be collected in the froth. After separation from the aqueous solution, the scandium content in the froth can be determined either spectrophotometrically with Arsenazo III or with electrothermal AAS. Optimum values have been worked out for the amount of surfactant (sodium oleate or cetyltrimethyl-ammonium bromide, CTAB) needed for the most favourable recovery of scandium and for attaining a precision of 0.40 g from 500 ml solution in the subsequent determination with electrothermal AAS. Sodium oleate is superior to CTAB for scandium enrichment.
Dedicated to Prof. Dr. W. Fresenius on the occasion of his 70th birthday
Presented at the China-Japan Bilateral Conference on Analytical Chemistry, Changchun, China, Sept. 14–17th, 1983 相似文献
4.
Masahiko Miyauchi Yoshinori Kawaguchi Akira Harada 《Journal of inclusion phenomena and macrocyclic chemistry》2004,50(1-2):57-62
-Cyclodextrin having cinnamamide at 6- or 3-positions (6-CiNH--CD, 3-CiNH--CD) and -cyclodextrin with cinnamamide on 6-position (6-CiNH--CD) have been prepared. Supramolecular structures were formed in the solid state or aqueous solutions and characterized by measurements of NMR and vapor pressure osmometry (VPO). The results indicate that 6-CiNH--CD formed insoluble supramolecular polymers in the solid state, while 6-CiNH--CD and 3-CiNH--CD formed supramolecular complexes in aqueous solutions. 6-CiNH--CD was found to form a dimer in an aqueous solution. 3-CiNH--CD formed intermolecular complexes to give supramolecular polymers. The differences of the position of guest part on cyclodextrins caused to give a variety of supramolecular structures in aqueous solutions. 相似文献
5.
S. A. Darke S. E. Long C. J. Pickford J. F. Tyson 《Fresenius' Journal of Analytical Chemistry》1990,337(3):284-289
Summary The performances of two alternative sample introduction methods for use with Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) have been evaluated for the analysis of the same sample material. The laser ablation sample introduction system is based on a Nd:YAG laser to which an x-y-z translational sampling head had been added. A study has been made of a number of parameters which affect the performance of the system to find the optimum operating conditions. The slurry introduction system involved aspirating the slurries into the plasma using a de Galan nebuliser and a Scott-type spray chamber arrangement. A study has been made of the parameters which control the production of stable homogeneous slurries. Initial particle size measurements have been carried out on the slurried samples to show how this affects this method of sample introduction. Results are presented for the analysis of a South African reference material rock sample (SARM 5) by ICP-OES with both laser ablation and slurry nebulisation sample introduction and some preliminary results for the analysis by ICP-MS with laser ablation introduction. Semi-quantitative results are obtained for laser ablation ICP-OES as only one matrix matched standard is used. However, the agreement between the results obtained for slurry nebulisation and the certificate value is poor. It is suggested by comparison with previous studies that this may be due to particle size effects. Encouraging results were obtained for the determination of trace elements by laser ablation ICP-MS. 相似文献
6.
A new gamma-ray spectrum catalog and library for PGAA 总被引:1,自引:0,他引:1
Zs. Révay G. L. Molnár T. Belgya Zs. Kasztovszky R. B. Firestone 《Journal of Radioanalytical and Nuclear Chemistry》2001,248(2):395-399
New measurements have been performed at the PGAA facility at the Budapest Research Reactor (BRR) in order to create a prompt -ray catalog for qualitative and quantitative analysis. The measured spectra were accurately analyzed by HYPERMET-PC. Prompt -ray energies and associated -ray production cross-sections have been determined by internal standardization. The resulting catalog contains prompt -ray data from neutron capture and other reactions such as (n,), and decay -ray data from short-lived reaction products. Data have been measured for nearly all stable elements, from hydrogen to uranium. Generally, data for several isotopes are given, to enable isotopic analysis as well. The whole library, including elemental spectra, will be available as a book. 相似文献
7.
G. V. Shevchuk Yu. S. Vollerner A. S. Shashkov V. Ya. Chirva 《Chemistry of Natural Compounds》1992,27(5):597-603
Proofs are given of the structures of two new glycosides of the furostan series isolated from the leaves of the plantNolina microscarpa S. Wats. (family Dracaenaceae). Nolinofuroside D is (25S)-furost-5-ene-1,3,22,26-tetraol 1-O--D-galactopyranoside 26-O--D-glucopyranoside (I), and nolinofuroside F is (25S)-furost-5-ene-1,3,22,26-tetraol 1-O--D-fucopyranoside 26-O--D-glucopyranoside 3-O--L-rhamnopyranoside (VII). The latter was characterized as its 22-O-methyl ether (VIII). Nolinofuroside E (IV) has the structure of (25S)-furost-5-ene-1,3,22,26-tetraol 26-O--glucopyranoside 1-O-[O--L-rhamnopyranosyl-(12)--D-fucopyranoside], which followed from the structure of the fermentation product (VI). The products of the fermentation of the above-named compounds were present in the plant in only trace amounts. Only one of them — nolinospiroside D (III) — has not been described previously. This monoside of the spirostan series is (25S)-spirost-5-ene-1,3-diol 1-O--D-galactopyranoside.M. V. Frunze Simferopol' State University. Institute of Chemistry of Plant Substances, Uzbek Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 678–686, September–October, 1991. 相似文献
8.
Nerea Goyenechea Miguel Sánchez Itziar Vélaz Carmen Martín Cristina Martínez-Ohárriz Arantxa Zornoza 《Journal of inclusion phenomena and macrocyclic chemistry》2002,44(1-4):283-288
The interactions of nabumetone (NAB) with -cyclodextrin (-CD) and-cyclodextrin (-CD) were studied in aqueous solution by meansof phase-solubility analysis. Solid dispersions of NAB with -cyclodextrin(-CD), -cyclodextrin (-CD), methyl- (M-CD),hydroxypropyl-cyclodextrin (HP-CD) were prepared by coevaporationand kneading and also by coprecipitation in the case of -CD. X-ray diffractometry, thermal analysis and infrared spectroscopy (FTIR) were used to study the possibility of complexation of the drug with the different cyclodextrins. Solid dispersions of nabumetone with -CD showed a remarkable improvement in the dissolution rate of nabumetone. 相似文献
9.
Summary The quantitative determination of trace elements in human blood serum by Total Reflection X-Ray Fluorescence Analysis (TXRF) is influenced by absorption- and reflection-effects caused by the organic (proteins) and inorganic (P, S, Na, K, Ca, Cl) matrices. To minimize these effects we have developed a sample preparation technique based on the decomposition of the organic matrix and followed by the separation of the trace elements from the organic matrix by ion-exchange. The described method enables the simultaneous determination of K (1584 g), Ca (666 g), Fe (22 g), Cu (9.6 g), Zn (8.8 g), Se (0.97 g), Sn (1.3 g), Pb (0.12 g) and Rb (1.6 g) (obtained values in parentheses).
Herrn Prof. Dr. G. Tölg zum 60. Geburtstag gewidmet 相似文献
Herrn Prof. Dr. G. Tölg zum 60. Geburtstag gewidmet 相似文献
10.
P. Schramel 《Journal of Radioanalytical and Nuclear Chemistry》1993,168(1):215-221
Problems in trace element analysis in the biomedical and environmental field are discussed, especially for the most interesting elements, as well as adequate analytical techniques for their analysis. The state of the art for the relevant elements, the recommended methods as well as the new speciation analysis are briefly described. Besides these points, quality control, becoming more and more important to improve the reliability of analytical data, is discussed. 相似文献
11.
H. Güven N. Güngör A. Alemdar C. Ş. Özben 《Journal of Radioanalytical and Nuclear Chemistry》1996,214(4):269-276
Instrumental neutron activation analysis was applied to the determination of trace elements in a Na-bentonitic clay. The irradiation was done in the Triga Mark II type reactor of ITU Nuclear Energy Institute. The sample was irradiated in two steps for short- and long- lived isotopes. After irradiation, spectra were taken using a germanium detector, multichannel analyzer Canberra System 100 and a fitting program called Sampo 90. The spectra of short-lived isotopes were analyzed to determine Al, Mg, Na, K, Ca, Ti elements and Mn, V trace elements. The spectra of long-lived isotopes were analyzed to determine Sc, Br, Sb, Cs, La, Ce, Sm, Yb, Hf, Pa, Np trace elements. 相似文献
12.
Peter Wilhartitz R. Krismer H. Hutter M. Grasserbauer S. Weinbruch H. M. Ortner 《Fresenius' Journal of Analytical Chemistry》1995,353(5-8):524-532
Applying a recently developed three dimensional SIMS imaging technique major differences in the distribution of trace elements in ultra high purity Mo and W have been found. In the electron beam melted material severe grain boundary segregation of trace elements have occurred whereas in the hot pressed material trace elements have been present as precipitates with a size of 5–15 m. Guided by the results of the 3D-SIMS images and the advantages of the sintering process a material with homogeneous distribution of trace elements has been developed and characterised. To test the applicability for the microelectronics industry, sputtering targets have been manufactured out of this new material and layers with a thickness of 350 nm have been sputterdeposited on silicon. The quality of these layers, with respect to particle emission and the distribution of trace elements, was evaluated by EPMA and 3D-SIMS imaging. Further improvement of the sintering process led to a material with a completely homogeneous distribution of C, H, N, O and S to minimise the outgassing and diffusion of impurities.Abbreviations BSE
Back scattered electron
- EPMA
Electron probe micro analysis
- GAAS
Graphite furnace atomic absorption spectrometry
- GDMS
Glow discharge mass spectrometry
- ICP-AES
Inductively coupled plasma atomic emission spectrometry
- ICP-MS
Inductively coupled plasma mass spectrometry
- SIMS
Secondary ion mass spectrometry
- ULSI
Ultra large scale integration 相似文献
13.
A simple and novel electrogenerated chemiluminescence (ECL) method for the determination of sulfite has been developed based on the energy transfer ECL process. It was found that a weak ECL signal of sulfite was electrochemically generated on a platinum electrode in neutral aqueous solution. The signal was strongly enhanced by rhodamine B as an energy receptor and further enhanced by the neutral surfactant Tween 80. In 0.10M phosphate buffer solution (pH=7.5) containing 2.0×10–6gmL–1 rhodamine B and 0.4% (v/v) Tween 80, the ECL response to the concentration of sulfite at a potential of 0.82V was linear over a range of 1.0×10–7gmL–1 to 8.0×10–6gmL–1, and the detection limit was 5×10–8gmL–1. The relative standard deviation (n=11, 1.0×10–6gmL–1) was 3.8%. The proposed method has been successfully applied to the determination of sulfite in pharmaceutical injections and white sugar samples. 相似文献
14.
A method has been developed for the determination of the concentration of basic sites on white and deeply colored solid porous materials, which is based on the displacement of adsorbed benzoic acid by acetic acid. The determination is rapid and gives results comparable with those obrained by the titration with benzoic acid using thymolphthalein as indicator.
. . , , , .相似文献
15.
Under kinetically controlled conditions, phenanthrene is converted to 9-hydroxyphenanthrene by acid hexacyanoferrate(III) in 90% aqueous acetic acid. The value of –4.0 indicates that the reaction proceeds via the formation of a cation radical intermediate.
15* 相似文献
(III) 9- 90%- . =–4,00, -.
15* 相似文献
16.
M. Sh. Yagpharov 《Journal of Thermal Analysis and Calorimetry》1982,23(1-2):111-121
The literature data on the degree of crystallinity of non-deformed poly(ethylene terephthalate) measured at various temperatures have been subjected to comparative analysis. There is no correlation between the results obtained by the different methods. The reason for this is shown to be the imperfections in the methods of determining the degree of crystallinity, which do not provide the true composition of the crystalline phase. Consideration has been paid to the validity of the main principles involved in the thermal method of determining the degree of crystallinity, so as to eliminate the imperfections in the existing methods and to provide the correct value of the mass of the crystalline phase. The phase composition of PET has been analyzed by the thermal method at different temperatures and conditions of crystallization. A marked difference from the literature data is observed in the range of low temperatures.
Zusammenfassung Eine vergleichende Analyse der Literaturangaben bezüglich des bei verschiedenen Temperaturen gemessenen Kristallisationsgrades von nicht-deformiertem Poly(äthylen-terephthalat) wurde durchgeführt. Zwischen den mit verschiedenen Methoden erhaltenen Ergebnissen besteht keine Korrelation. Es wurde gezeigt, daß der Grund hierfür in der Unvollkommenheit der Methoden zur Bestimmung des Kristallisationsgrades liegt, da diese nicht die wahre Zusammensetzung der Kristallinen Phase angeben. Die Gültigkeit der wichtigsten Prinzipien, welche die thermische Bestimmung des Kristallisationsgrades unter Ausschaltung der Unvollkommenheit der bestehenden Methoden gewährleisten und den richtigen Wert der Masse der kristallinen Phase angeben, wurden in Erwägung gezogen. Die Analyse der Phasenzusammensetzung von PET wurde durch die thermische Methode bei verschiedenen Temperaturen und Kristallisationsbedingungen durchgeführt. Ein deutlicher Unterschied zu den Literaturangaben kann im Bereich der niedrigen Temperaturen beobachtet werden.
. , , . , , . , , . . .相似文献
17.
N. M. Ostrovskii L. A. Karpova V. K. Duplyakin 《Reaction Kinetics and Catalysis Letters》1984,26(3-4):279-284
Catalysts with nonuniform distribution of the catalytically active component (Pt) over their porous support (Al2O3) have been studied. A nonuniform activity distribution changes not only the reaction rate but also the kinetics can be different on these catalysts.
(Pt) (Al2O3). , , .相似文献
18.
Tohru Kanno Yukitoshi Tatsumoto Masayoshi Kobayashi 《Reaction Kinetics and Catalysis Letters》1991,43(1):237-241
Ethylene hydroformylation over a Nafion-supported rhodium catalyst has been studied under atmospheric pressure in the temperature range of 100–135 °C, using the transient response method.
, , 100–135°C, .相似文献
19.
C. Karunakaran K. Ganapathy P. Ramasasamy 《Reaction Kinetics and Catalysis Letters》1989,40(2):369-374
The perborate oxidation of quinol in aqueous acetic acid is first order with respect to perborate, zero order with respect to quinol, and first order with respect to H+. The oxidation is faster than H2O2 oxidation. Breakdown of protonated perboric acid is suggested as the rate-limiting step.
, H+. . , , , .相似文献
20.
The thermal decomposition of ammonium uranates precipitated from uranyl nitrate solution on the addition of aqueous ammonium hydroxide and hexamine under various conditions has been studied by means of thermogravimetry, differential thermal analysis, infrared spectroscopy and X-ray diffraction. Although all precipitates show the composition corresponding to UO3 · NH3 · H2O, the precipitates with hexamine give X-ray diffraction patterns designed as types I and II, in which type I is similar to the precipitates with ammonia. As a result, it is concluded that ammonium uranates thermally decompose to amorphous UO3 at about 400°, and transform to U3O8 via-UO3 and/or-UO3, latter being formed in the case of type II only.
Zusammenfassung Die thermische Zersetzung von unter verschiedenen Bedingungen durch wässrige Lösungen von Ammoniumhydroxid und Hexamin aus Uranylnitrat-Lösung gefällten Ammoniumuranaten wurde mittels TG, DTA, IR-Spektroskopie und Röntgendiffraktometrie untersucht. Obwohl die Zusammensetzung aller Niederschläge der Formel UO3 · NH3 · H2O entspricht, geben die mit Hexamin gefällten Niederschläge die als Typ I und II bezeichneten Röntgendiffraktogramme, von denen das des Typs I ähnlich dem der mit Ammoniak gefällten Niederschlage ist. Es wird festgestellt, daß Ammoniumuranate bei 400° thermisch zu amorphen UO3 zersetzt werden und sich über-UO3 und/oder-UO3—wobei beim Typ II nur das letztere gebildet wird — in U3O8 umwandeln.
, , - - , . @2 UO3 · NH3 · H2O, , - I II. . , 400° UO3 U3O8 -UO3 -UO3. II.相似文献