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991.
A. Damarupurshad R. J. Hart J. P. F. Sellschop H. O. Meyer 《Journal of Radioanalytical and Nuclear Chemistry》1997,219(1):33-39
Instrumental neutron activation analysis (INAA) has been applied to the analysis of 62 small (0.01–0.5 carat), single, inclusion-bearing and inclusion-free diamonds from South Africa, Brazil and Colorado. Up to 40 elements were detected at the ppb and ppt levels in individual diamonds of the eclogitic (basaltic affinity) and the peridotitic (ultramafic) paragenesis. The data obtained in this study can be used to distinguish between diamonds from the eclogitic and peridotitic parageneses and provides geochemical information on the environment in which diamonds crystallize. Further, the technique may prove to be useful in fingerprinting diamonds of different provenance areas. 相似文献
992.
A. N. Kornev O. S. Donnikova V. V. Semenov Yu. A. Kurskii 《Russian Chemical Bulletin》1995,44(1):145-148
A method for preparing (trichloromethyl)organosilanes by the catalytic decarboxylation of the corresponding trichloroacetoxysilanes RMe2SiOC(O)CCl3 (R = Me, ClCH2, Ph, Me3Si, and H) has been developed. The method involves heating the starting compounds without a solvent in the presence of a catalyst (quaternary ammonium salts or potassium salts with the addition of crown ethers). Tertiary amines (Et3N, Bu3N) catalyze this reaction only when heating is carried out in donor aprotic solvents (THF, acetonitrile) in the presence of oxygen. Thermal decomposition of (trichloroacetoxy)organosilanes, in contrast to catalytic decarboxylation, begins at a higher temperature and yields a mixture of products.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 150–153, January, 1995. 相似文献
993.
Summary Pesticides may be detected following thin-layer chromatography by spraying the chromatogram with a reagent which forms a-complex with the pesticide. The effect of various pesticide structures and substituents in choosing a suitable-complexing reagent is discussed, as well as the effect of these factors in influencing the colour of the complex formed. Quantitative analyses may be performedin situ on the thin-layer chromatogram and positive identification of the-complexed compounds may be made by mass spectrometry. The procedure should be applicable for formulation analysis or studies of pesticide decomposition.
Issued as NRCC No. 13120. 相似文献
Zusammenfassung Zum Nachweis von Pestiziden besprüht man deren Dünnschichtchromatogramme (DC) mit einem zur Bildung eines-Komplexes geeigneten Reagens. Die Bedeutung verschiedener Pestizidstrukturen und -Substituenten bei der Wahl eines solchen Reagens wurde erörtert; ebenso der Einfluß der genannten Faktoren auf die Farbe des Komplexes. Quantitative Bestimmungen lassen sich unmittelbar auf dem DC, Nachweise der einzelnen komplexierten Verbindungen mit Hilfe der Massenspektrometrie durchführen. Das Verfahren eignet sich zur Strukturanalyse sowie zur Untersuchung von Pestizidabbauproblemen.
Issued as NRCC No. 13120. 相似文献
994.
Distribution of some major and trace elements in Danube Delta lacustrine sediments and soil 总被引:2,自引:0,他引:2
L. C. Dinescu E. Steinnes O. G. Duliu C. Ciortea T. E. Sjobakk D. E. Dumitriu M. M. Gugiu M. Haralambie 《Journal of Radioanalytical and Nuclear Chemistry》2004,262(2):345-354
Sediment cores collected from lakes Mesteru and Furtuna (eastern part), Sontea channel and soil samples collected from Caraorman
bar, all located in the Danube Delta, were analyzed for 42 elements (Ag, Al, As, Be, Na, Mg, P, S, K, Ca, Sc, Ti, V, Cr, Mn,
Fe, Co, Ni, Cu, Zn, Ga, As, Se, Br, Rb, Sr, Y, Mo, Ag, Cd, In, Sn, Sb, Cs, Ce, Hf, Hg, Tl. Pb, Bi, Th. U) by instrumental
neutron activation analysis (INAA), thick target proton induced X-ray emission (TT-PIXE) and inductively coupled plasma-mass
spectrometry (ICP-MS). The INAA and TTPIXE yielded total concentrations whereas the ICP-MS data reflected the fractions soluble
in 14M HNO3. The ICP-MS data exhibited surface enrichment relative to the lower part of the sediment core of Cu, Zn, As, Ag, Cd, In,
Sn, Sb, Hg, Tl, Pb, and Bi, most prominently by Cd and Hg. Their vertical distribution in the investigated cores generally
reflected the pollution history of recent sediments in Danube delta, showing a steady increase until the end of the 1980s
followed by a slow decrease after 1990. The vertical profiles of most remaining elements were characterized by a relatively
uniform distribution along the cores. In some cases, the concentrations of As, Cd, Cu, Cr, Mn, Ni and Pb exceeded minimum
thresholds of safety, as defined by the Romanian regulations. The elemental composition of the sediment below 20 cm depth
(total concentrations) was similar to that of the upper continental crust (UCC) for most elements. Values distinctly higher
than UCC were observed for As, Sb (factor ~5) and Cr, Ni, Cu (factor 2 to 3). The nitric acid soluble element concentrations
in the soil samples in some cases showed increased values at the surface as compared to 30 cm depth, either due to air pollution
or to the action of plants. In no case a large contribution to the topsoil from atmospheric deposition was evident, indicating
that the surface contamination of the sediments was mainly by riverine transport.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
995.
The hydrosilylation reaction of octa(hydrido)silsesquioxane with ω‐halo‐1‐alkenes and other unsaturated substrates allows attachment of 8 long‐chain functionalized alkyls on the cubic Si8O12 skeleton. Pt/C and H2PtCl6 have been adopted as the catalysts, the yields being 74–98% for compounds 2–9 . For terminal alkenes, the hydrosilylation follows the anti‐Markonikov's rule. The morphological state of 2–9 ranges from viscous liquid to crystalline materials. The pyrolysis results indicate that 7 , a material of hard spherical core and soft flexible shell, may likely act as nanometer‐size ball bearings up to more than 400 °C. The X‐ray structure of 9 reveals that the molecule is required to possess a center of symmetry crystallographically. The linear arms on 9 , except for two of them, are virtually all‐trans in conformation, not counting the ω‐C‐Cl bond. 相似文献
996.
997.
Conclusions A number of metal alloys in the Sb-Cd-Zn system was studied for the first time by the NQR method on the121,123Sb nuclei. The constants of the quadrupole bond and the asymmetry parameter of the compounds ZnSb were determined.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No; 7. pp. 1638–1640, July, 1977. 相似文献
998.
999.
1000.
V. A. Logvinenko B. I. Peshchevitsky O. V. Gegola 《Journal of Thermal Analysis and Calorimetry》1980,18(3):463-467
The major causes leading to the apparent compensation effect (lgA=aE+b) at the thermal decomposition of one and the same substance in a series of experimental conditions (varying of the mass of the sample, of the heating rate, of disperseness, and at different distances from the equilibrium) were discussed. It was found that the appearance of a compensation effect at the study of the thermal decomposition of one and the same substance demonstrates the incorrect setup of the experiment, resulting in erroneous values calculated for the kinetic parameters.
Zusammenfassung Die Hauptursachen, welche zum scheinbaren Kompensationseffekt (lgA=aE+b) der thermischen Zersetzung ein und derselben Substanz führen, wurden unter verschiedenen Versuchsbedingungen untersucht: unter Änderung der Probenmasse, der Aufheizgeschwindigkeit, der Dispersität und der Entfernung vom Gleichgewicht. Es wurde festgestellt, daß das Auftreten eines Kompensationseffekts bei der Untersuchung der thermischen Zersetzung ein und derselben Substanz auf die unrichtige Durchführung des Experiments hinweist, die zur Berechnung falscher Werte der kinetischen Parameter führt.
Résumé On a étudié les causes principales de l'effet de compensation apparent (lgA=aE+ +b) lors de la décomposition thermique de la même substance dans différentes conditions expérimentales, en faisant varier notamment la masse du prélèvement, la vitesse du chauffage, la dispersion et l'écart à l'équilibre. On a trouvé que l'apparition d'un effet de compensation lors de l'étude de la décomposition thermique de la même substance résultait de l'exécution incorrecte de l'expérience qui mène à des valeurs fausses lors du calcul des paramètres cinétiques.
, (lg A=aE+b) : , , , . , , .相似文献