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Mass Spectrometric Results (mass + spectrometric_result)
Selected AbstractsCharacterization of non-covalent complexes of rutin with cyclodextrins by electrospray ionization tandem mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2004Mingquan Guo Abstract Electrospray ionization tandem mass spectrometry (ESI-MSn) and the phase solubility method were used to characterize the gas-phase and solution-phase non-covalent complexes between rutin (R) and ,-, ,- and ,-cyclodextrins (CDs). The direct correlation between mass spectrometric results and solution-phase behavior is thus revealed. The order of the 1 : 1 association constants (Kc) of the complexes between R and the three CDs in solution calculated from solubility diagrams is in good agreement with the order of their relative peak intensities and relative collision-induced dissociation (CID) energies of the complexes under the same ESI-MSn condition in both the positive and negative ion modes. Not only the binding stoichiometry but also the relative stabilities and even binding sites of the CD,R complexes can be elucidated by ESI-MSn. The diagnostic fragmentation of CD,R complexes, with a significant contribution of covalent fragmentation of rutin leaving the quercetin (Q) moiety attached to the CDs, provides convincing evidence for the formation of inclusion complexes between R and CDs. The diagnostic fragment ions can be partly confirmed by the complexes between Q and CDs. The gas-phase stability order of the deprotonated CD,R complexes is ,-CD,R > ,-CD,R > ,-CD/R; ,-CD seems to bind R more strongly than the other CDs. Copyright © 2004 John Wiley & Sons, Ltd. [source] Electrospray and matrix-assisted laser desorption/ionization mass spectral characterization of linear single nylon-6 oligomersJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2001Lu Shan Abstract Synthetic nylon-6 single molecular mass oligomers were studied by matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) mass spectrometry. These oligomers, considered as model compounds for the study of nylon-6 polymers, gave good mass spectrometric results using both MALDI and ESI. In spite of the gentle nature of both techniques, the MALDI and ESI spectra showed evidence of end-group cleavage from the oligomer chains. MALDI-MS was found to give similar fragmentation patterns for all of the oligomer samples. An increase in doubly charged ion signals with increasing oligomer mass was observed in the ESI mass spectra, as was end-group fragmentation. Signals from oligomer clusters were observed in ESI-MS for the dimer, tetramer and hexamer, most likely due to non-covalent bonding among the low-mass oligomer molecules. Copyright © 2001 John Wiley & Sons, Ltd. [source] Limitations of mass spectrometric methods for the characterization of polydisperse materials,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2010Alan A. Herod This paper is a review of work on the characterization of coal liquids and petroleum residues and asphaltenes over several decades in which various mass spectrometric methods have been investigated. The limitations of mass spectrometric methods require exploration in order to understand what the different analytical methods can reveal about environmental pollution by these kinds of samples and, perhaps more importantly, what they cannot reveal. The application of mass spectrometry to environmental problems generally requires the detection and determination of the concentration of specific pollutants released into the environment by accident or design. The release of crude petroleum or coal liquids into the environment can be detected and tracked during biodegradation processes through specific chemicals such as alkanes or polyaromatic hydrocarbons (PAHs). However, petroleum asphaltenes are polydisperse materials of unknown mass range and chemical structures and, therefore, there are no individual chemicals to detect. It is necessary to determine methods of detection and the ranges of mass of such materials. This can only be achieved through fractionation to reduce the polydispersity of the initial sample. Comparison of mass spectrometric results with results from an independent analytical method such as size-exclusion chromatography with a suitable eluent is advisable to confirm that all the sample has been detected and mass discrimination effects avoided. Copyright © 2010 John Wiley & Sons, Ltd. [source] Synthesis of phase-pure SnS particles employing dithiocarbamate organotin(IV) complexes as single source precursors in thermal decomposition experimentsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 9 2010D. C. Menezes Abstract Preparation of tin(II) sulfide, semiconductor material, has been accomplished by thermal decomposition of easily prepared organotin dithiocarbamate complexes: [Sn{S2CNEt2}2Ph2] (1), [Sn{S2CNEt2}Ph3] (2), [Sn{S2CNEt2}3Ph] (3) and [Sn{S2CN(C4H8)}2Bu2] (4). Phase-pure tin(II) sulfide has been obtained by pyrolysis of these precursors at 350 °C in N2. Thermogravimetric analysis, X-ray powder diffraction, scanning electron microscopy, X-ray electron probe microanalysis and 119Sn Mössbauer spectroscopy revealed that the complexes decompose in a single and sharp step (1 and 2), or in pseudo-single stage (3 and 4), to produce SnS. We have also measured the bandgap energies of the residues using electronic spectroscopy in the solid state and the result relates well to that in the literature for SnS, 1.3 eV. A decomposition mechanism was also proposed for each complex based on electrospray ionization tandem mass spectrometric results. The synthetic method used in this work might be useful for the preparation of pure SnS on a large scale. Copyright © 2010 John Wiley & Sons, Ltd. [source] |