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1.
S. Mlinkó I. Gács K. Payer J. Ottinger E. Dobis 《Journal of Radioanalytical and Nuclear Chemistry》1977,35(2):321-331
In this paper an automatic apparatus designed for the radioactivity measurement of14C-labelled organic compounds in the gaseous phase is described. The labelled organic compounds are combusted in a mixture
of argon and oxygen. After combustion the oxygen content of the gas is eliminated by passing it through a copper packing.
The water and heteroelements present are also removed and the radioactive carbon dioxide gas is swept by argon carrier gas
into a piston-type counter tube. In the counter tube the piston forming a dividing wall moves forward in accordance with the
rate of combustion and sweeping, and thus sucks the gases leaving the combustion tube into the effective tube volume. The
anode wire is carried by a reel located in the piston and a spring device ensures its stretched state. At the end of the sweeping
period methane is fed into the counter tube and the activity of the argon—methane—carbon dioxide mixture is measured in the
limited proportional region. Manual and automatic operation is possible. The piston-type counter tube provides possibility
for strandardization by means of extrapolation and for measurement of absolute activities. 相似文献
2.
Summary A procedure has been developed for the activity measurement of tritium-labelled organic compounds in the gas phase. The organic compounds are pyrolysed in hydrogen carrier gas at 1150° and the decomposition products are swept through a carbon packing in accordance with the principle of the oxygen determination developed byUnterzaucher andBürger. The radioactive gas mixture obtained from the sample is swept by the hydrogen carrier gas flowing continuously through the reactor into a proportional counter tube, after the addition of propanebutane counter gas. By closure of the counter tube at a suitable moment, the radioactive gas is quantitatively trapped in the counter tube. The activity is measured in the limited proportional region. No memory effect occurs. The preparation of the sample requires 12 minutes; the relative standard deviation of analysis is <0.5%.
Zusammenfassung Ein Verfahren zur Aktivitätsbestimmung bei tritium-markierten organischen Verbindungen in der Gasphase wurde ausgearbeitet. Die organischen Substanzen werden in Wasserstoff als Trägergas bei 1150° pyrolysiert. Die Zersetzungsprodukte werden wie bei der Sauerstoffbestimmung nachUnterzaucher bzw.Bürger über eine Kohleschicht geleitet. Das radioaktive Gas-gemisch aus der Probe gelangt mit dem kontinuierlich strömenden Trägergas in ein Proportionalzählrohr, nachdem Propan-Butan-Zählgas zugesetzt wurde. Man schließt das Zählrohr im richtigen Augenblick, um das radioaktive Gas quantitativ zu erfassen. Die Aktivität wird im Proportionalbereich gemessen. Ein Memory-Effekt tritt nicht auf. Die Vorbereitung der Probe beansprucht 12 Minuten. Die relative Standardabweichung ist kleiner als 0,5%.相似文献
3.
A sample preparation method developed for the simultaneous liquid scintillation assay of tritium and35S in doubly labelled organic materials is described. The sample is burnt in a stream of oxygen and the radioactive isotope
carriers formed are collected separately for individual counting.35S content of the sample is measured as a dilute sulfuric acid solution, while the tritium is counted as water. The procedure
is free of cross-contamination and memory effect, provides quantitative analytical recovery, and the final solutions ready
for counting are obtained in twelve minutes. 相似文献
4.
Grald Monard Michel Loos Vincent Thry Kristofor Baka Jean-Louis Rivail 《International journal of quantum chemistry》1996,58(2):153-159
A coherent computational scheme on a very large molecule in which the subsystem that undergoes the most important electronic changes is treated by a semiempirical quantum chemical method, though the rest of the molecule is described by a classical force field, has been proposed recently. The continuity between the two subsystems is obtained by a strictly localized bond orbital, which is assumed to have transferable properties determined on model molecules. The computation of the forces acting on the atoms is now operating, giving rise to a hybrid classical quantum force field (CQFF ) which allows full energy minimization and modeling chemical changes in large biomolecules. As an illustrative example, we study the short hydrogen bonds and the proton-exchange process in the histidine-aspartic acid system of the catalytic triad of human neutrophil elastase. The CQFF approach reproduces the crystallographic data quite well, in opposition to a classical force field. The method also offers the possibility of switching off the electrostatic interaction between the quantum and the classical subsystems, allowing us to analyze the various components of the perturbation exerted by the macromolecule in the reactive part. Molecular dynamics confirm a fast proton exchange between the three possible energy wells. The method appears to be quite powerful and applicable to other cases of chemical interest such as surface reactivity of nonmetallic solids. © 1996 John Wiley & Sons, Inc. 相似文献
5.
I. Gács S. Mlinkó K. Payer Z. Vargay L. Ötvös D. Bánfi T. Palágyi 《Journal of Radioanalytical and Nuclear Chemistry》1978,46(1):109-119
An isotope analytical procedure and an automatic instrument developed for the determination of tritium in organic compounds
and biological materials by internal gas counting are described. The sample is burnt in a stream of oxygen and the combustion
products including water vapour carrying the tritium are led onto a column of molecular sieve-5A heated to 550 °C. Tritium
is retained temporarily on the column, then transferred into a stream of hydrogen by isotope exchange. After addition of butane,
the tritiated hydrogen is led into an internal detector and enclosed there for radioactivity measurement. The procedure, providing
quantitative recovery, is completed in five minutes. It is free of memory effect and suitable for the determination of tritium
in a wide range of organic compounds and samples of biological origin. 相似文献
6.
S. Hermann P. Neuschul V. Lucas L. Bracaloni F. Berger M. Kochmann H. Kunz A. Lévêque J. Moulin C. van Zijp R. Kleinert K. Bambach T. H. Rider D. Payer K. Peták H. Kaiser H. Will Ch. F. Poe C. H. Hampshire G. R. Page W. Karaffa-Korbutt L. Rosenthaler L. D. Korosstischewskaja Marguerite van Hauwert H. Leonhardt R. Klockmann R. P. Jacquemain H. Mistroff G. F. Reddish D. Bartos J. Buchgraber E. Klarmann V. A. Shternov A. Mossini M. G. Vergez 《Analytical and bioanalytical chemistry》1938,114(9-10):368-375
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An absorption/detection system is described for the determination of carbon at and below microgram detection level. The carbon dioxide formed by combustion of an organic substances (solid or in solution) is led into a simple absorption/detection system containing 2.00 cm3 of an ethanolic 2 M solution of 3-methoxypropylamine. The conductivity of the carbamate solution formed is measured by means of platinum electrodes built in the absorption tube, and the integrated d.c. voltage signal obtained is fed to a precision digital voltmeter. Detector response is linear up to 6.6 μg of carbon, and the detection limit is 2 × 10?2 μg. A single determination takes 5 min. Precision was found to be better than +? 1.0% (P-=95%) for 1–6 μg or carbon. 相似文献
9.
J. E. Hansen B. I. Rickett J. H. Payer H. Ishida 《Journal of Polymer Science.Polymer Physics》1996,34(4):611-621
The degradation of poly-N-vinylimidazole films on copper substrates was studied by Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy. Infrared measurements on samples heated at 300°C for 15 minutes revealed that the oxidation of the polymer was accelerated by the copper. X-ray photoelectron spectroscopy showed that a layer of copper oxide was formed on top of the oxidized film. Copper ions were also detected within the polymer layer. © 1996 John Wiley & Sons, Inc. 相似文献
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