共查询到20条相似文献,搜索用时 78 毫秒
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应用碰撞诱导解离技术研究了苯自身化学电离条件下和苯化学电离(甲苯为反应气)条件下离子-分子反应产物m/z155和156离子的碰撞诱导解离(CID)破裂特性,并与化学电离条件下质子化联苯生成m/z155离子的CID碎裂反应相比较,获得了苯离子1-分子反应产物m/z155和156离子的结构信息。 相似文献
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水中氯苯类污染物的顶空液相微萃取 GC-MS法测定 总被引:3,自引:0,他引:3
研究了用顶空液相微萃取GC-MS法测定水中的痕量氯苯类有机污染物。通过实验选择正辛醇为萃取剂,考察了萃取剂的体积、萃取温度、萃取时间、搅拌速度、样品顶空体积以及盐效应等对萃取的影响。在最佳萃取和测定条件下,方法的线性范围为0.1~800μg/L,检出限(S/N=3)为0.05~0.1μg/L。用本方法测定了实际样品及回收率,结果满意。 相似文献
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水体中有机污染物的分析 总被引:5,自引:0,他引:5
采用大孔径树脂吸附法对地表水和地下水中微量有机污染物进行富集,再用GC—MS法进行分析,其中地表水样品中共检出有机污染物42种,两处地下水样品中分别检出有机污染物9种和10种。对地表水与地下水之间相关性的研究表明,地下水样品中捡出的有机污染物都包括在地表水所含有机污染物的范围之内,地下水中含有有机污染物与地表水受到污染存在支接联系。 相似文献
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GC-MS测定人血清中酞酸酯类环境污染物 总被引:7,自引:0,他引:7
为了解酞酸酯类环境污染物在人血清中的含量水平。采用毛细管柱气相色谱-质谱联用法的选择离子检测(GC-MS-SIR)技术,结合有机溶剂提取,高速离心去蛋白和低温浓缩的方法测定103份健康人血清中酞酸二丁酯(di--nbutyl phthalate,DBP)和酞酸二异辛酯[di-(2-ethyl-hexyl)phthalate,DEHP]。测定结果提示酞酸酯类环境污染物已进入人血清,DBP约为7.10 mg.L-1,DEHP约为6.78 mg.L-1,大部分人体内已有一定的污染负荷。 相似文献
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Dr. George N. Khairallah Dr. Alan T. Maccarone Dr. Huong T. Pham Timothy M. Benton Dr. Tony Ly Dr. Gabriel da Silva Prof. Stephen J. Blanksby Prof. Richard A. J. O'Hair 《Angewandte Chemie (International ed. in English)》2015,54(44):12947-12951
Although the deleterious effects of ozone on the human respiratory system are well‐known, many of the precise chemical mechanisms that both cause damage and afford protection in the pulmonary epithelial lining fluid are poorly understood. As a key first step to elucidating the intrinsic reactivity of ozone with proteins, its reactions with deprotonated cysteine [Cys?H]? are examined in the gas phase. Reaction proceeds at near the collision limit to give a rich set of products including 1) sequential oxygen atom abstraction reactions to yield cysteine sulfenate, sulfinate and sulfonate anions, and significantly 2) sulfenate radical anions formed by ejection of a hydroperoxy radical. The free‐radical pathway occurs only when both thiol and carboxylate moieties are available, implicating electron‐transfer as a key step in this reaction. This novel and facile reaction is also observed in small cys‐containing peptides indicating a possible role for this chemistry in protein ozonolysis. 相似文献
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Tandem MS techniques have been used to examine the formation of cluster ions derived from organotin compounds of environmental significance. The cluster formation was based on the addition of either water or methanol molecules (common HPLC solvents) to a cationic species derived from the organotin compound. For the compounds and conditions studied, cluster adducts were only observed from trisubstituted tin cations. The results show that, in high-pressure ionization methods used in the interface between HPLC and MS, the tin atom may be associated with a range of ions depending on the system parameters, and that care should be taken if selection ion monitoring (SIM) is to be used. 相似文献
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This paper reports on a mass spectrometric study of the neutral and ionic species in a low-pressure rf discharge sustained in a C2H4-SiH4 mixture diluted in helium. It is shown that C2H4 is readily decomposed into C2H
2
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and C2H3. The formation of secondary products such as C4H2, C4H4, and C4H6 is observed and confirms the presence of C2H2 in the discharge. Methylsilane (CH3SiH3) and ethylsilane (C2H5SiH3) are also synthesized in this discharge. It is also observed that the major ions C2H
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, C3H
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, SiH
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, Si2H
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, SiCH
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, SiC2H
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, and SiC2H
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are not representative of the direct ionization of neutral species. Their formation is thus interpreted on the basis of ion-molecule reactions. 相似文献
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Accretion Product Formation from Self‐ and Cross‐Reactions of RO2 Radicals in the Atmosphere 下载免费PDF全文
Dr. Torsten Berndt Wiebke Scholz Bernhard Mentler Lukas Fischer Prof. Hartmut Herrmann Prof. Markku Kulmala Prof. Armin Hansel 《Angewandte Chemie (International ed. in English)》2018,57(14):3820-3824
Hydrocarbons are emitted into the Earth's atmosphere in very large quantities by human and biogenic activities. Their atmospheric oxidation processes almost exclusively yield RO2 radicals as reactive intermediates whose atmospheric fate is not yet fully unraveled. Herein, we show that gas‐phase reactions of two RO2 radicals produce accretion products composed of the carbon backbone of both reactants. The rates for accretion product formation are very high for RO2 radicals bearing functional groups, competing with those of the corresponding reactions with NO and HO2. This pathway, which has not yet been considered in the modelling of atmospheric processes, can be important, or even dominant, for the fate of RO2 radicals in all areas of the atmosphere. Moreover, the vapor pressure of the formed accretion products can be remarkably low, characterizing them as an effective source for the secondary organic aerosol. 相似文献
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Dr. Denis Lesage Prof. Anne Milet Dr. Antony Memboeuf Jérôme Blu Dr. Andrew E. Greene Prof. Jean‐Claude Tabet Dr. Yves Gimbert 《Angewandte Chemie (International ed. in English)》2014,53(7):1939-1942
The mechanism of the Pauson–Khand reaction has been studied by mass spectrometry and it has been found, through ion‐molecule reaction with 13CO, that the carbon monoxide incorporated into the product cyclopentenone is one that has been retained within the complex. Theoretical and kinetic calculations support this finding, which provides a complementary explanation for the effect of Pauson–Khand promoters. 相似文献
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Julia E. Fleckenstein Konrad Koszinowski Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(46):12745-12753
Solutions of butylzinc iodide in tetrahydrofuran, acetonitrile, and N,N‐dimethylformamide were analyzed by electrospray ionization mass spectrometry. In all cases, microsolvated butylzinc cations [ZnBu(solvent)n]+, n=1–3, were detected. The parallel observation of the butylzincate anion [ZnBuI2]? suggests that these ions result from disproportionation of neutral butylzinc iodide in solution. In the presence of simple bidentate ligands (1,2‐dimethoxyethane, N,N‐dimethyl‐2‐methoxyethylamine, and N,N,N′,N′‐tetramethylethylenediamine), chelate complexes of the type [ZnBu(ligand)]+ form quite readily. The relative stabilities of these complexes were probed by competition experiments and analysis of their unimolecular gas‐phase reactivity. Fragmentation of mass‐selected [ZnBu(ligand)]+ leads to the elimination of butene and formation of [ZnH(ligand)]+. In marked contrast, the microsolvated cations [ZnBu(solvent)n]+ lose the attached solvent molecules upon gas‐phase fragmentation to produce bare [ZnBu]+, which subsequently dissociates into [C4H9]+ and Zn. This difference in reactivity resembles the situation in organozinc solution chemistry, in which chelating ligands are needed to activate dialkylzinc compounds for the nucleophilic addition to aldehydes. 相似文献
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Bilge Baytekin Dr. H. Tarik Baytekin Dr. Uwe Hahn Dr. Werner Reckien Dr. Barbara Kirchner Prof. Dr. Christoph A. Schalley Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(29):7139-7149
The mass spectrometric characterization of Fréchet‐type dendrons is reported. In order to provide the charges necessary for electrospray ionization, dendrons bearing an OH group at the focal point can be deprotonated and observed in the negative ion mode. Alternatively, the corresponding bromides can be converted to quaternary ammonium ions that can easily be detected in the positive mode. If the latter ions are subjected to collision‐induced dissociation experiments, a fragmentation cascade begins with the dissociation of the focal amine. The focal benzyl cation quickly decomposes in a fragmentation cascade from the focal point to the periphery until the peripheral benzyl (or naphthylmethyl) cations are formed. Five different mechanisms are discussed in detail, three of which can be excluded based on experimental evidence. The cascade fragmentation is reminiscent of self‐immolative dendrimers. 相似文献
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Gemma Vall‐llosera Michael A. Huels Prof. Dr. Marcello Coreno Dr. Antti Kivimäki Dr. Katarzyna Jakubowska Marek Stankiewicz Prof. Dr. Elisabeth Rachlew Prof. Dr. 《Chemphyschem》2008,9(7):1020-1029
We have measured the synchrotron‐induced photofragmentation of isolated 2‐deoxy‐D ‐ribose molecules (C5H10O4) at four photon energies, namely, 23.0, 15.7, 14.6, and 13.8 eV. At all photon energies above the molecule′s ionization threshold we observe the formation of a large variety of molecular cation fragments, including CH3+, OH+, H3O+, C2H3+, C2H4+, CHxO+ (x=1,2,3), C2HxO+ (x=1–5), C3HxO+ (x=3–5), C2H4O2+, C3HxO2+ (x=1,2,4–6), C4H5O2+, C4HxO3+ (x=6,7), C5H7O3+, and C5H8O3+. The formation of these fragments shows a strong propensity of the DNA sugar to dissociate upon absorption of vacuum ultraviolet photons. The yields of particular fragments at various excitation photon energies in the range between 10 and 28 eV are also measured and their appearance thresholds determined. At all photon energies, the most intense relative yield is recorded for the m/q=57 fragment (C3H5O+), whereas a general intensity decrease is observed for all other fragments— relative to the m/q=57 fragment—with decreasing excitation energy. Thus, bond cleavage depends on the photon energy deposited in the molecule. All fragments up to m/q=75 are observed at all photon energies above their respective threshold values. Most notably, several fragmentation products, for example, CH3+, H3O+, C2H4+, CH3O+, and C2H5O+, involve significant bond rearrangements and nuclear motion during the dissociation time. Multibond fragmentation of the sugar moiety in the sugar–phosphate backbone of DNA results in complex strand lesions and, most likely, in subsequent reactions of the neutral or charged fragments with the surrounding DNA molecules. 相似文献
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Chiara Salvitti Federico Pepi Anna Troiani Giulia de Petris 《Molecules (Basel, Switzerland)》2021,26(23)
The reactivity of [NaL·ClO2]− cluster anions (L = ClOx−; x = 0–3) with sulphur dioxide has been investigated in the gas phase by ion–molecule reaction experiments (IMR) performed in an in-house modified Ion Trap mass spectrometer (IT-MS). The kinetic analysis revealed that SO2 is efficiently oxidised by oxygen-atom (OAT), oxygen-ion (OIT) and double oxygen transfer (DOT) reactions. The main difference from the previously investigated free reactive ClO2− is the occurrence of intracluster OIT and DOT processes, which are mediated by the different ligands of the chlorite anion. This gas-phase study highlights the importance of studying the intrinsic properties of simple reacting species, with the aim of elucidating the elementary steps of complex processes occurring in solution, such as the oxidation of sulphur dioxide. 相似文献
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Dr. Davide Corinti Dr. Alessandro Maccelli Prof. Barbara Chiavarino Dr. Markus Schütz Dr. Aude Bouchet Prof. Otto Dopfer Prof. Maria Elisa Crestoni Prof. Simonetta Fornarini 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(33):e202200300
The structure of an isolated Ag+(benzylamine) complex is investigated by infrared multiple photon dissociation (IRMPD) spectroscopy complemented with quantum chemical calculations of candidate geometries and their vibrational spectra, aiming to ascertain the role of competing cation-N and cation-π interactions potentially offered by the polyfunctional ligand. The IRMPD spectrum has been recorded in the 800–1800 cm−1 fingerprint range using the IR free electron laser beamline coupled with an FT-ICR mass spectrometer at the Centre Laser Infrarouge d'Orsay (CLIO). The resulting IRMPD pattern points toward a chelate coordination (N-Ag+-π) involving both the amino nitrogen atom and the aromatic π-system of the phenyl ring. The gas-phase reactivity of Ag+(benzylamine) with a neutral molecular ligand (L) possessing either an amino/aza functionality or an aryl group confirms N- and π-binding affinity and suggests an augmented silver coordination in the product adduct ion . 相似文献