Ionization time

The molecular weights and molecular weight distributions (MWD) of phenolic oligomers have been evaluated using gel permeation chromatography (GPC),23,24 NMR spectroscopy,25 vapor pressure osmometry (VPO),26 intrinsic viscosity,27 and more recently matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS).28... 

Maleamic acid, cyclization of, 293 Maleic anhydride, 59 Maleimido azine, 307 Manganese diacetate catalysts, 71 Mark-Houwink-Sakurada equation, 57 Material safety data sheets (MSDSs), 246 Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS), 385, 388 McGrath, J. E., 327 MDI isomers, 210 MDIs. See Methylene diphenyl diisocyanates (MDIs)... 

Matrix-assisted laser desorption ionization time-of-flight mass spectrometry... 

The anion 19 has been generated by high-energy collision of the p-pentazoylphenolate anion with an inert gas [109] and by laser desorption ionization time-of-flight mass spectroscopy of sohd p-dimethylaminophenylpentazole [110]. N AsP, NjSbF, and [Nj]jSnF have been used by Gordon, Christe et al. [Ill] in their attanpt to observe N F. 

Starting from 27, cyclo-Cig was prepared in the gas phase by laser flash heating and the neutral product, formed by stepwise elimination of three anthracene molecules in retro-Diels-Alder reactions, was detected by resonant two-photon-ionization time-of-flight mass spectrometry [23]. However, all attempts to prepare macroscopic quantities of the cyclocarbon by flash vacuum pyrolysis using solvent-assisted sublimation [50] only afforded anthracene and polymeric material. 

Considering these situations, the observation of molecular weights, particularly by matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF MASS), is essential [33]. The operation is simple and enables us to observe the molecular ion peaks of CPOs with molecular weights exceeding 10,000. The quahty of the measurement is strongly dependent on the choice of the matrix. Therefore, the search for the best matrix for each CPO should be pursued. 

Anke, G. H., Thomas, M., Frank, G., Reiner, S., Helge, B., Markus, K., and Monika, K. (2008). Challenging the problem of clostridial identification with matrix-assisted laser desorption and ionization-time-of-fight mass spectrometry (MALDl-TOF MS). Anaerobe 14, 242-249. 

Whittal, R.M., Russon, L.M., and Li, L., Development of liquid chromatogra-phy-mass spectrometry using continuous-flow matrix-assisted laser desorption ionization time-of-flight mass spectrometry, /. Chromatogr. A, 794, 367, 1998. 

Choudhary, G., Chakel, J., Hancock, W., Torres-Duarte, A., McMahon, G., and Wainer, I., Investigation of the potential of capillary electrophoresis with offline matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for clinical analysis examination of a glycoprotein factor associated with cancer cachexia, Anal. Chem. 71, 855, 1999. 

Krishnamurthy, T. Ross, P. Rajamani, U. D. Detection of pathogenic and non-pathogenic bacteria by matrix assisted laser desorption/ionization time-of-flight mass spectrometry. Rapid Comm. Mass Spectrom. 1996,10,883-888. 

Elhanany, E. Barak, R. Fisher, M. Kobiler, D. Altboum, Z. Detection of specific Bacillus anthracis biomarkers by matrix-assisted laser desorption/ionization time-of-flight mass sspectrometry. Rapid Commun. Mass Spectrom. 2001,15,2110-2116. 

Other pattern recognition strategies have been used for bacterial identification and data interpretation from mass spectra. Bright et al. have recently developed a software product called MUSE, capable of rapidly speciating bacteria based on matrix-assisted laser desorption ionization time-of-flight mass spectra.13 MUSE constructs a spectral database of representative microbial samples by using single point vectors to consolidate spectra of similar (not identical) microbial strains. Sample unknowns are then compared to this database and MUSE determines the best matches for identification purposes. In a... 

Bright, J. J. Claydon, M. A. Soufian, M. Gordon, D. B. Rapid typing of bacteria using matrix-assisted laser desorption ionization time of flight mass spectrometry and pattern recognition software. J. Microbiol. Meth. 2002,48,127-138. 

Lee, H. Williams, S. K. R. Wahl, K. L. Valentine, N. B. Analysis of whole bacterial cells by flow field-flow fractionation and matrix-assisted laser desorption/ ionization time-of-flight mass spectrometry. Anal. Chem. 2003, 75,2746-2752. 

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