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51.
Ch Engelmann G. Filippi J. Gosset F. Moreau 《Journal of Radioanalytical and Nuclear Chemistry》1977,37(2):559-570
The photonuclear reactions used for this isotopic analysis are as follows:16O(γ, n)15O threshold energy 15.7 MeV;18O(γ, p)17N threshold energy 16.3 MeV.15O is a pure β+ emitter of half-life 2.03 minutes, whereas17N presents a 4.2 second neutron emission. The principle of the method is founded on the simultaneous measurement of the above
characteristic radioactivities, the intensities of which are proportional to the respective quantities of16O and18O present in the irradiated sample. The potentialities of this new oxygen isotope analysis method, based on the use of an
electron accelerator, are described. Detection limit of 0.1 μg18O is easily attainable. The equipment designed and built to industrialise this technique is described. It allows a hundred
samples to be analysed automatically, the accelerator, detection instruments and pneumatic transfer circuits being controlled
by a logic system linked to an electronic chronometer. 相似文献
52.
An efficient metal-free procedure for the synthesis of tertiary amines by the reductive amination of carbonyl compounds is reported, which allows a convergent access to sterically hindered amines of the general formulas NR(R′)2 and NRR′R″. The mild and operationally simple protocol uses the Hantzsch ester for transfer hydrogenation and catalytic amounts of thiourea for imine activation. 相似文献
53.
54.
Lohmann W Dötzer R Gütter G Van Leeuwen SM Karst U 《Journal of the American Society for Mass Spectrometry》2009,20(1):138-145
On-line electrochemistry/liquid chromatography/mass spectrometry (EC/LC/MS) was employed to mimic the oxidative metabolism of the fungicide boscalid. High-resolution mass spectrometry and MS/MS experiments were used to identify its electrochemical oxidation products. Furthermore, the introduction of a second electrochemical cell with reductive conditions provided important additional information on the oxidation products. With this equipment, hydroxylation, dehydrogenation, formation of a covalent ammonia adduct, and dimerization were detected after initial one-electron oxidation of boscalid to a radical cation. On-line reaction with glutathione yielded different isomeric covalent glutathione adducts. The results of the electrochemical oxidation are in good accordance with previously reported in vivo experiments, showing that EC/LC/MS is a useful tool for studying biotransformation reactions of various groups of xenobiotics. 相似文献
55.
Photonuclear activation with 18 and 35 MeV bremsstrahlung beams and gamma ray spectrometry has been used to determine the
concentrations of 14 elements in human hair. A careful study of interferences made possible a nondestructive analysis with
practical limits of detection between 0.1 and 100 μg·g.
相似文献
56.
Synthesis and Structure of Tetrafluoroaurates(III) MI[AuF4] with MI = Li, Rb Single crystal investigations on Rb[AuF4], light yellow, confirm the tetragonal unit cell (K[BrF4]-type) with a = 618.2(1) and c = 1191(1) pm, Z = 4, space group I 4/mcm-D (No. 140). Li[AuF4], light yellow too, crystallizes monoclinic with a = 485.32(7), b = 634.29(8), c = 1004.43(13) pm, β = 92.759(12), Z = 4; space group P 2/c-C (No. 13). The structure of Li[AuF4] is related to the Rb[AuF4]-type of structure. 相似文献
57.
58.
The determination of carbon and nitrogen in molybdenum and of carbon, nitrogen and oxygen in tungsten, is described. The analytical techniques applied were charged-particle activation (carbon, nitrogen and oxygen), photon activation (carbon and oxygen), combustion (carbon) and vacuum-fusion extraction (nitrogen and oxygen). Chemical methods yielded upper limits in the 2-5 mug/g range. Activation analysis yielded 100 and 8 ng/g for carbon in molybdenum and tungsten respectively, 500 and 74 ng/g for nitrogen in molybdenum and tungsten respectively and 70 ng/g for oxygen in tungsten. The results obtained by charged-particle and photon activation agreed satisfactorily. 相似文献
59.
M. D. Engelmann L. A. Metz N. E. Ballou 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(2):201-204
Two
methods capable of near complete recovery of technetium adsorbed on charcoal
are presented. The first involves liquid extraction of the technetium from the
charcoal by hot 4M nitric acid. An average recovery of 98% (n=3) is
obtained after three rounds of extraction. The second method involves dry
ashing with air in a quartz combustion tube at 400-450 °C. This method yields
an average recovery of 96% (n=5). Other thermal methods were attempted, but
resulted in reduced recovery and incomplete material balance.</p>
</p> 相似文献
60.
Ch. Engelmann J. Gosset C. Grumet 《Journal of Radioanalytical and Nuclear Chemistry》1975,28(1-2):185-199
The activation methods, nuclear reactions and chemical separation processes used to determine traces of carbon, nitrogen and oxygen in the metals and semiconductors considered are described briefly. The results obtained are reviewed. They mainly concern the following analyses: (1) determination of carbon and oxygen in alkaline metals; (2) determination of nitrogen and oxygen in refractory metals; (3) determination of carbon, nitrogen and particularly oxygen in various other metals; (4) determination of these same elements in semiconducting materials. In some cases the concentrations measured by γ photon or charged particle activation methods are compared with the results obtained by other techniques. 相似文献