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91.
Jan Henk Marsman Berthold B. Breman Antonie A. C. M. Beenackers 《Journal of separation science》1993,16(3):141-147
The main problems with complete analysis of the components of fuel methanol, or in Fischer-Tropsch studies, are the several classes of compound present in the sample (permanent gases, water, alcohols, hydrocarbons), its wide range of components, its boiling point range, and the wide range of component concentrations. A flexible on-line GC method has been developed for kinetic study of catalyzed chemical reactions of hydrogen and oxides of carbon. The single capillary column, temperature programmed method was designed for complete analysis of reactants and products (hydrogen, carbon monoxide, carbon dioxide, water, C1-C10 hydrocarbons, and C1-C6 alcohols): a sample selection valve is used to switch between either the heated line used for input of the synthesis gases or the heated line used to transport reaction products from the reactor. Sample is introduced to the capillary column by means of a 10-port heated gas sampling valve with two external injection loops (0.07 and 1.95 cm3); this results in the determination of components over a wide range of concentrations in the sample (ppm to percentage levels). Helium from a pressure-controlled supply is used as carrier gas and detection of the components is performed by serial connection of thermal conductivity and flame ionization detectors. Peak identification is performed by mass spectrometry and by comparison of component retention times. The automated analytical equipment is integrated with a process control computer and delivers repeatable analytical results for the individual components (RSDs varying between 0.3 and 10% depending strongly on the concentration of the component and the accuracy of the determination of its peak area). 相似文献
92.
Henk Schierbeek Denise Rook Frans W. J. te Braake Kristien Y. Dorst Gardi Voortman Jean‐Philippe Godin Laurent‐Bernard Fay Johannes B. van Goudoever 《Rapid communications in mass spectrometry : RCM》2009,23(18):2897-2902
Determination of glutathione kinetics using stable isotopes requires accurate measurement of the tracers and tracees. Previously, the precursor and synthesized product were measured with two separate techniques, liquid chromatography/isotope ratio mass spectrometry (LC/IRMS) and gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). In order to reduce sample volume and minimize analytical effort we developed a method to simultaneously determine 13C‐glutathione as its dimeric form (GSSG) and its precursor [1‐13C]glycine in a small volume of erythrocytes in one single analysis. After having transformed 13C‐glutathione into its dimeric form GSSG, we determined both the intra‐erythrocytic concentrations and the 13C‐isotopic enrichment of GSSG and glycine in 150 µL of whole blood using liquid chromatography coupled to LC/IRMS. The results show that the concentration (range of µmol/mL) was reliably measured using cycloleucine as internal standard, i.e. with a precision better than 0.1 µmol/mL. The 13C‐isotopic enrichment of GSSG and glycine measured in the same run gave reliable values with excellent precision (standard deviation (sd) <0.3‰) and accuracy (measured between 0 and 5 APE). This novel method opens up a variety of kinetic studies with relatively low dose administration of tracers, reducing the total cost of the study design. In addition, only a minimal sample volume is required, enabling studies even in very small subjects, such as preterm infants. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
93.
94.
The extended Boltzmann equation introduced in previous papers is used to compute the torque exerted on a macroscopic sphere or cylinder placed in a dilute gas, when the mean free path of the gas molecules is small compared to the characteristic dimension of the sphere or cylinder. The usual hydrodynamic results are recovered in this kinetic theory calculation.Work supported in part by the National Science Foundation Grant No. CHE 77-16308. 相似文献
95.
Reactions of propargyl trimethyl silane with ω-ethoxy lactams 1a-c under the influence of boron trifluoride etherate afford ω-allenyl lactams 3a-c; 5-allenyl-2-pyrrolidinone is hydrolysed to γ-allenyl-GABA. 相似文献
96.
We present a transpose-free version of the nonsymmetric scaled Lanczos procedure. It generates the same tridiagonal matrix
as the classical algorithm, using two matrix–vector products per iteration without accessing AT. We apply this algorithm to obtain a transpose-free version of the Quasi-minimal residual method of Freund and Nachtigal
[15] (without look-ahead), which requires three matrix–vector products per iteration. We also present a related transpose-free
version of the bi-conjugate gradients algorithm.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
97.
Jan R. de Dobbelaere Erica L. van Zeeventer Jan W. de Haan Henk M. Buck 《Theoretical chemistry accounts》1975,38(3):241-244
INDO calculations have been performed for the activated complex of the [1, 5] H.-shift in 1,3-cyclohexadiene and 1,3,5-cycloheptatriene. During the migration in the cyclohexadiene system a homoconjugation was calculated between the carbon atoms C1 and C5. For cycloheptatriene it could be demonstrated that one double bond does not participate in the reaction. Activation enthalpies are related to (homo)conjugation in the transition state of the reaction for cyclic conjugated dienes and trienes. The electron density on the migrating hydrogen can be related to the electron affinity of the ring system in the transition state.[/p] 相似文献
98.
Henk Hiemstra Wim J. Klaver Marinus J. Moolenaar W.Nico Speckamp 《Tetrahedron letters》1984,25(47):5453-5456
The combination of a silicon directed N-acyliminium ion cyclization reaction and a subsequent SN2′ substitution of an imide nitrogen with lithium dimethyl cuprate constitutes a novel approach to functionalized transfused carbobicycles. 相似文献
99.
100.
Intramolecular reactions of acyclic N-acyliminium ions with allyl silanes, induced by protic or Lewis acid, lead to 3-vinylpyrrolidines or 3-vinylpiperidines. 相似文献