共查询到20条相似文献,搜索用时 812 毫秒
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2—羟基—4—邻苯二甲酰亚胺基丁酸的氢迁移反应 总被引:1,自引:0,他引:1
在甲烷为反应气的化学电离质谱条件下,质子化的2-羟基-4-邻苯二甲酰亚胺基丁酸的单分子质谱碎裂产生了m/z148的碎片离子,表明其碎裂过程发生了氢迁移反应,AM在分子轨道的理论计算结果为可能的质子化位置提供了理论依据;建立在氘代同位素标记和碰撞诱导解离实验的基础上,我们提出此离子的形成可能同时存在单氢迁移和双氢迁移,一些质谱图中的物征碎片中离子为可能的McLafferty重排和离子/中性(碎片)复 相似文献
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烷基苯磺酸盐的电喷雾离子化质谱和碰撞活化解离质谱-质谱分析 总被引:4,自引:0,他引:4
用正,负电喷雾电离(ESI)并结合碰撞活化解离(CAD)质谱法对烷基苯磺酸盐(ABS)进行鉴定,无论正,负离子化过程中均不出现快原子轰击质谱常见的碎片峰,由于没有复杂碎片峰的干扰,ESI-MS对分析ABS试样大为有利,正离子ESI-MS对支化ABS鉴定的灵敏度远低于负离子ESI-MS,用CAD-MS对ESI-ME谱各主要峰进行了归属,线型与支化ABS相对含量可以用负离子ESI-MS求出,负离子化ESI-MS是快速,有效和可靠的鉴定,ABS的方法。 相似文献
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Takashi Yokoyama Hirokazu Tsuji Takaomi Akamatsu Michio Zenki 《Analytical sciences》2004,20(4):657-662
The capillary electrophoretic behavior of 44 aromatic organic ions was investigated. The observed ionic radii (r(obs0)) for the aromatic organic ions were obtained from the electrophoretic mobilities of sodium tetraborate (pH 9.2), potassium tetraborate (pH 9.2), ammonium borate (pH 9.2), and trisodium phosphate (pH 11.7) buffers with zero ionic strength. The linear relationships between the r(obs0)) values and the ionic radii (r(calc)), calculated by either the AM1 or PM3 method, were determined for benzyltrialkylammonium and aromatic sulfonate ions. However, the r(obs0)) values were constant for the aromatic carboxylate ions in buffers, in spite of the different r(calc) values. This indicates that aromatic carboxylate ions, such as benzenecarboxylate, pyridinecarboxylate, naphthalenecarboxylate, and anthracenecarboxylate ions, migrate as planar ions in buffers, whereas aromatic sulfonate ions could migrate as approximately spherical ions. 相似文献
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The ionization pathways and ion mobility were determined for sets of structural isomeric and stereoisomeric non-polar hydrocarbons (saturated and unsaturated cyclic hydrocarbons and aromatic hydrocarbons) using a novel miniature differential mobility spectrometer with atmospheric-pressure photoionization (APPI) to assess how structural and stereochemical differences influence ion formation and ion mobility. The analytical results obtained using the differential mobility spectrometry (DMS) were compared with the reduced mobility values measured using conventional time-of-flight ion mobility spectrometry (IMS) with the same ionization technique.The majority of differences in DMS ion mobility spectra observed among isomeric cyclic hydrocarbons can be explained by the formation of different product ions. Comparable differences in ion formation were also observed using conventional IMS and by investigations using the coupling of ion mobility spectrometry with mass spectrometry (APPI-IMS-MS) and APPI-MS. Using DMS, isomeric aromatic hydrocarbons can in the majority of cases be distinguished by the different behavior of product ions in the strong asymmetric radio frequency (rf) electric field of the drift channel. The different peak position of product ions depending on the electric field amplitude permits the differentiation between most of the investigated isomeric aromatics with a different constitution; this stands in contrast to conventional IMS in which comparable reduced mobility values were detected for the isomeric aromatic compounds. 相似文献
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Y Habata M Ikeda S Yamada H Takahashi S Ueno T Suzuki S Kuwahara 《Organic letters》2012,14(17):4576-4579
Tetra-armed cyclens bearing aromatic side arms were prepared by the reductive amination of cyclen with substituted benzaldehydes. When equimolar amounts of Ag(+) ions were added to the ligands, the aromatic rings covered the Ag(+) ions incorporated in the ligand cavities, as if the aromatic ring "petals" caught the Ag(+) ions in the way an insectivorous plant (Venus flytrap) catches insects. The ligands are called "argentivorous molecules". Evidence of intramolecular Ag(+)-π interactions in solution and in the solid state is reported. 相似文献
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Peifeng Hu Curt Sorensen Michael L. Gross 《Journal of the American Society for Mass Spectrometry》1995,6(11):1079-1085
Aromatic side chains on amino acids influence the fragmentations of cationic complexes of doubly charged metal ions and singly deprotonated peptides. The metal ion interacts with an aromatic side chain and binds to adjacent amide nitrogens. When fragmentation occurs, this bonding leads to the formation of abundant metal-containing a-type ions by reactions that occur at the sites of amino acids that contain the aromatic side chain. Furthermore, formation of metal-containing immonium ions of the amino acids that contain the aromatic side chain also are formed. The abundant a-type ions may be useful in interpretation strategies in which it is necessary to locate in a peptide the position of an amino acid that bears an aromatic side chain. 相似文献
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大港减压渣油超临界萃取萃余残渣结构特征研究 总被引:1,自引:1,他引:0
〗通过超临界萃取方法对大港减压渣油进行深度窄馏分切割,利用钌离子催化氧化(RICO)对其抽余残渣进行选择性降解,对降解生成的混合物进行分离,其中非挥发性羧酸进行甲酯化处理,挥发性羧酸进行苯甲酰甲酯化,最后分别利用GC-MS等方法进行定性定量分析。结果表明,大港减压渣油超临界萃取萃余残渣分子中含有大量与芳环相连的正构烷基侧链和桥接芳环的聚亚甲基链,芳环的缩合程度小于利用结构族组成等分析方法分析大港减压渣油沥青质得到的结果。大港减压渣油超临界萃取萃余残渣的共价结构信息可对该原料的加工和优化利用提供指导。 相似文献
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Small cyclophanes containing aromatic groups and dialkyl ammonium ions were created as model systems of the cation-pi complexes found at some protein binding domains. The hosts had different shapes in order to investigate the effect the arrangement of ammonium ions to aromatic surfaces has on their reactivity. pK(a) values of the hosts were substantially different in DMSO or (95/5) DMSO/D(2)O solutions, which showed that the ions existed in different environments of the hosts. Electrostatic charges, as determined by density functional calculations, revealed that the magnitude of a cationic charge depends on its position relative to an aromatic ring. Association constants of the hosts bound to the sodium salt of N-acetyl phenylalanine in d(6)-DMSO and in (95/5) d(6)-DMSO/D(2)O solutions were inversely proportional to the magnitude of the hosts' acidity constants. These results suggest that the magnitude of the positive charge for cationic groups of cation-pi complexes is reduced by being associated with electron-rich faces of aromatic rings. The aromatic rings, however, lessen the desolvation penalty that must be overcome for ligand binding, giving an overall more favorable association. 相似文献
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Charles Eric Brown Peter Kovacic Kenneth J. Welch Robert B. Cody R. E. Hein James A. Kinsinger 《Journal of polymer science. Part A, Polymer chemistry》1988,26(1):131-148
Laser desorption/Fourier transform mass spectra of poly(phenylene sulfide), polyaniline, poly(vinyl phenol), polypyrene, poly(p-phenylene), poly(1-methyl-2,5-pyrrolylene), poly(1-phenyl-2,5-pyrrolylene), and poly(2,5-thienylene) are compared. Poly(phenylene sulfide) fragments at C? S bonds during analysis, but rearrangement is minor. Evidence is found for dibenzothiophene moieties within the polymer chains. Unambiguous determination of the structure of polyaniline is not possible. Rearrangement appears to accompany chain scission. Completely aromatic polymers do not undergo similar reactions during analysis. Species with more carbons than can be accounted for by an integer multiple of six-membered rings arise from side reactions during dehydrocoupling of aromatic monomers. Carbon clusters, which are observed in the spectra of some aromatic polymers, appear to arise from laser volatilization and multiphoton ionization of large polynuclear components that are formed during synthesis. Negative ions of about 40–120 carbons and positive ions with about 120–400 atoms are detected. The results also suggest that the physical dimensions of some polymer molecules might be measured by Fourier transform mass spectrometry. 相似文献
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In this study, a novel stir bar sorptive extraction (SBSE) based on monolithic material (SBSEM) was prepared. The monolithic material was obtained by in situ copolymerization of vinylpyrrolidone and divinylbenzene in the presence of a porogen solvent containing cyclohexanol and 1-dodecanol with azobisisobutyronitrile as initiator. The influences of polymerization conditions on the extraction efficiencies were investigated, using phenol and p-nitrophenol as detected solutes. The monolithic material was characterized by various techniques, such as elemental analysis, scanning electron microscopy, mercury intrusion porosimetry, infrared spectroscopy. Polycyclic aromatic hydrocarbons were used to investigate the extraction efficiencies of SBSEM for apolar analytes. Hormones, aromatic amines and phenols were selected as test analytes to investigate the extraction efficiencies of SBSEM for weakly and strongly polar compounds. The results showed that the new SBSEM could enrich the above-mentioned organic compounds effectively. It is worthy to mention that the SBSEM can enrich some heavy metal ions, such as Cu2+, Pb2+, Cr3+ and Cd2+, through coordination adsorption. To our best knowledge, that is the first to use SBSE to enrich heavy metal ions. 相似文献
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Li L Chiarelli MP Branco PS Antunes AM Marques MM Gonçalves LL Beland FA 《Journal of the American Society for Mass Spectrometry》2003,14(12):1488-1492
Product ion spectra from thirteen C8-substituted alkylaniline adducts of guanine and deoxyguanosine were generated using electrospray ionization and quadrupole ion trap mass spectrometry and studied to investigate the possibility of differentiating isomeric adduct structures based upon the relative abundances of fragment ions derived from the alkylaniline-modified guanine bases (BH2+ ions). The structural discrimination of the BH2+ ions formed by attachment of isomeric alkylanilines to the C8 position of guanine is a challenging problem because the ions tend to yield product ion spectra that are qualitatively identical upon collisional activation. In this study, a statistical method, referred to as a similarity index, was used to compare the product ion spectra of isomeric BH2+ ions and differentiate their structures. All the adducts investigated could be distinguished from SIs calculated using 5–6 product ions. These results suggest that a searchable database of product ion spectra may be created and used to characterize DNA adducts from aromatic amines whenever they are detected at levels amenable to mass spectral analysis. 相似文献
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Susan D. Richardson John M. McGuire Alfred D. Thruston George L. Baughman 《Journal of mass spectrometry : JMS》1992,27(3):289-299
Eight monosulfonated and disulfonated azo dyes were analyzed using liquid secondary ion mass spectrometry/tandem mass spectrometry, in the negative ion mode, under low-energy collision conditions (110–150 eV). Many structurally characteristic fragment ions were obtained, several of which have not been reported previously using other mass spectrometric techniques. Among the structurally important ions observed were those due to loss of SO2, SO3 and various aromatic substituents, such as NO2 and NHCOCH3. Losses of N2 were also proposed. In addition, product ions due to cleavage at the azo linkage were observed, and also SO3? and HSO3? ions. Several of the azo cleavage product ions detected did not contain sulfonate groups. Possible pathways for the formation of product ions are proposed. The structural information obtained should help to better characterize and identify sulfonated azo dyes in the future. 相似文献