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31.
S Jürschik B Agarwal T Kassebacher P Sulzer CA Mayhew TD Märk 《Journal of mass spectrometry : JMS》2012,47(9):1092-1097
In this work, we illustrate the application of proton transfer reaction mass spectrometry (PTR-MS) in the field of food and drink safety. We present proof-of-principle measurements of four different drinks (water, tea, red wine and white wine) each spiked separately with four different date rape drugs (chloral hydrate, tricholorethanol, γ-butyrolactone and butanediol). At first, the ideal PTR-MS operating conditions (reduced electric field strength and monitoring the most abundant [fragment] ion) for detection of the drugs were determined utilizing a time-of-flight-based PTR-MS instrument. We then dissolved small quantities of the drugs (below the activation threshold for effects on humans) into the various types of drinks and detected them using a quadrupole-based PTR-MS instrument via two different sampling methods: (1) dynamic headspace sampling and (2) direct liquid injection. Both methods have their advantages and drawbacks. Only with dynamic headspace sampling can rape drug contaminations be detected within a timeframe of seconds, and therefore, this method is the most promising use of PTR-MS as a fast, sensitive and selective monitor for the detection of food and drink contamination. Copyright ? 2012 John Wiley & Sons, Ltd. 相似文献
32.
Transparent Boundary Conditions for Split-Step Padé Approximations of the One-Way Helmholtz Equation
In this paper, we generalize the nonlocal discrete transparent boundary condition introduced by F. Schmidt and P. Deuflhard (1995, Comput. Math. Appl.29, 53–76) and by F. Schmidt and D. Yevick (1997, J. Comput. Phys.134, 96–107) to propagation methods based on arbitrary Padé approximations of the two-dimensional one-way Helmholtz equation. Our approach leads to a recursive formula for the coefficients appearing in the nonlocal condition, which then yields an unconditionally stable propagation method. 相似文献
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In contrast to Fe+/diol complexes, gas-phase dehydrogenation of the corresponding FeII alkoxides, [FeO(CH2)nCH2OH]+, is a highly specific process in the course of which oxidation of the terminal OH group takes place. Based on labeling studies, this is the exclusive mechanism for n = 2 and 3 (Scheme: path ); for higher homologues, as for example [FeOf(CH2)7CH2OH]+, the labeling data demonstrate that an additional mechanism is operative, involving the dehydrogenation of internal positions of the alkyl chain (path ). The Fe+-mediated oxidation –CH2OH → –CHO +H2: constitutes one of the rare examples of O-H bond activation by late cationic transition-metal ions. 相似文献
36.
It is demonstrated for the first time that the site-selectivity for the Fe+-mediated C? H bond activation of aldimines R1N?CHR2 (R1, R2 = alkyl) involves the alkyl chain R1 by a factor ≥ 12 in comparison to the alkenyl part R2. This finding explains previous observations that dehydrogenation of intermediates formed by alkene loss from either R1 or R2 of R1N?CHR2/Fe+ preferentially involves the alkyl part. 相似文献
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Falk Meutzner Dr. Matthias Zschornak Dr. Artem A. Kabanov Tina Nestler Dr. Tilmann Leisegang Prof. Vladislav A. Blatov Prof. Dirk C. Meyer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(36):8623-8629
We have created a set of crystalline model structures exhibiting straight lines of Al3+ connected to chalcogenides (O2−, S2−, and Se2−) connected to metal cations of varying valence (Sr2+, Y3+, Zr4+, Nb5+, and Mo6+). They were relaxed with density functional theory computations and analysed by Bader partitioning. As Al3+ ions are supposed to strongly interact with their atomic environment, we studied the electron density topology induced by higher-valent cations in the extended chemical neighbourhood of Al. In fact, we found a general decrease of ionic charges and an increasing displacement of the chalcogenides towards higher-valent ions for the heavier chalcogens. Therefore, we comprehensively screened S- and Se-containing compounds for candidates theoretically exhibiting low migration barriers for Al3+ ions by using Voronoi–Dirichlet partitioning and bond valence site energy calculations. The basis for this search is the Inorganic Crystal Structure Database. Indeed, we could extract six promising candidates with low Al3+ migration barriers. which are even lower than the barriers for any other element inside of these materials. This will encourage efforts towards preparing suitable Al3+ conductors. 相似文献
39.
Denifl S Vizcaino V Märk TD Illenberger E Scheier P 《Physical chemistry chemical physics : PCCP》2010,12(20):5219-5224
Electron attachment to CO? clusters performed at high energy resolution (0.1 eV) is studied for the first time in the extended electron energy range from threshold (0 eV) to about 10 eV. Dissociative electron attachment (DEA) to single molecules yields O(-) as the only fragment ion arising from the well known (2)Π(u) shape resonance (ion yield centered at 4.4 eV) and a core excited resonance (at 8.2 eV). On proceeding to CO? clusters, non-dissociated complexes of the form (CO?)(n)(-) including the monomer CO?(-) are generated as well as solvated fragment ions of the form (CO?)(n)O(-). The non-decomposed complexes appear already within a resonant feature near threshold (0 eV) and also within a broad contribution between 1 and 4 eV which is composed of two resonances observed for example for (CO?)(4)(-) at 2.2 eV and 3.1 eV (peak maxima). While the complexes observed around 3.1 eV are generated via the (2)Π(u) resonance as precursor with subsequent intracluster relaxation, the contribution around 2.2 eV can be associated with a resonant scattering feature, recently discovered in single CO? in the selective excitation of the higher energy member of the well known Fermi dyad [M. Allan, Phys. Rev. Lett., 2001, 87, 0332012]. Formation of (CO?)(n)(-) in the threshold region involves vibrational Feshbach resonances (VFRs) as previously discovered via an ultrahigh resolution (1 meV) laser photoelectron attachment method [E. Leber, S. Barsotti, I. I. Fabrikant, J. M. Weber, M.-W. Ruf and H. Hotop, Eur. Phys. J. D, 2000, 12, 125]. The complexes (CO?)(n)O(-) clearly arise from DEA at an individual molecule within the cluster involving both the (2)Π(u) and the core excited resonance. 相似文献
40.
From dysfunction to bis-function: on the design and applications of functionalised ionic liquids 总被引:3,自引:0,他引:3
Fei Z Geldbach TJ Zhao D Dyson PJ 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(8):2122-2130
Some of the recent developments concerning the synthesis, properties and applications of functionalised ionic liquids are highlighted. Various strategies are presented, including functionalisation of the cation, anion or both cation and anion in the same ionic liquid, leading to what has been termed dual-functionalised ionic liquids. Particular attention is given to the application of functionalised ionic liquids as reaction media, to stabilise nanoparticles/modify surfaces and to generate porous materials. 相似文献