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  • 1
    Publication Date: 1990-09-01
    Print ISSN: 0003-2700
    Electronic ISSN: 1520-6882
    Topics: Chemistry and Pharmacology
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  • 2
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 108 (1977), S. 191-197 
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Mono-, di- and trichlorophenyl (4-pyridyl) ketones and a selection of their 3-pyridyl isomers follow similar mass spectral fragmentation paths. In the case of the phenyl (4-pyridyl) ketones the major primary fragmentation reaction of the intense molecular ion is the loss of the pyridyl group, while the corresponding 3-pyridyl ketones decay primarily by cleavage of the aryl—Cl bond or the aryl—CO bond.
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  • 4
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Some isomeric hydrocarbons with nearly identical mass spectra show significant differences in the spectra of neutral fragments, these spectra being determined by measuring the decompositions of metastable ions.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 98 (1967), S. 423-430 
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Zusammenfassung Die Struktur des Nitritacidium-Ions1 kann nach einer Interpretation vonSeel mit der Mesomerie zwischen zwei Grenzzuständen A und B (s. S. 428) erklärt werden. Es ist anzunehmen, daß sich bei einer Verminderung der Aktivität des Wassers der Resonanzzustand des Ions in Richtung von A nach B verschiebt. In sehr schwach perchlorsaurer, wäßriger Lösung läßt sich die Gleichgewichtskonstante der Bildung des Nitritacidium-Ions aus salpetriger Säure und Wasserstoffion aus kinetischen Daten vonHermann Schmid näherungsweise berechnen. In sehr stark perchlorsaurer, wäßriger Lösung läßt sich diese Gleichgewichtskonstante unter Verwendung der SäurefunktionJ 0 aus Gleichgewichtsmessungen des Salpetrigsäurezerfalles ermitteln. (Der gefundene Wert stimmt mit den vonSeel und vonDeno, Berkheimer, Evans undPeterson aus optischen Untersuchungen erhaltenen Werten und mit dem kürzlich vonGerhard Schmid undU. Neumann mit Hilfe der NO/NO+-Elektrode gemessenen Wert größenordnungsmäßig überein.) Der vonChallis undRidd gefundene „Mediumeffekt” bei der Diazotierung aromatischer Amine in perchlorsaurer, wäßriger Lösung kann durch die oben erwähnte Verschiebung in der Resonanzstruktur des Nitritacidium-Ions erklärt werden.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 121 (1990), S. 393-401 
    ISSN: 1434-4475
    Keywords: Nitro-PAH ; GC/MS ; Urban air ; Wood combustion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wurde eine Routinemethode zur Identifizierung und Quantifizierung von mononitrierten polycyclischen aromatischen Kohlenwasserstoffen in Umweltproben entwickelt. Zur Vortrennung der Proben wurde eine Flüssig-flüssig-Verteilung im Mikromaßstab zwischen Dimethylformamid und Cyclohexan und eine HPLC-Auftrennung an Silicagel-Säulen angewandt. Diese Aufarbeitungsmethode erwies sich gleichzeitig als zeit- und lösungsmittelsparend. Die Identifizierung und Quantifizierung der Nitro-PAHs erfolgt mittels GC/ECD und GC/MS im „selected ion monitoring“-Modus. Der Analysenvorgang wurde unter Verwendung von Standardsubstanzen durch Änderung der verschiedensten Parameter in den einzelnen Analysenschritten optimiert. Praktisch angewandt wurde die vorliegende Methode schließlich zur Untersuchung von Proben des Standardstaubs NBS Standard Reference Material SRM 1649 „Urban Dust“, von Stadtluft an einer verkehrsreichen Kreuzung in Wien und von Emissionen verschiedener Holzverbrennungsanlagen.
    Notes: Summary A routine method for the identification and quantification of mononitrated polycyclic aromatic hydrocarbons in environmental samples has been developed. Micro-scale liquid-liquid partition between dimethylformamide and cyclohexane and HPLC on normal-phase silica gel columns are used for clean-up of samples. This preconcentration scheme is time-saving and uses a minimal amount of solvents. Identification and quantification are performed by GC/ECD and GC/MS in the “selected ion monitoring” mode. The analytical scheme has been optimized under use of standard substances by variation of several parameters in different steps of the analysis. The method was applied to the NBS Reference Material SRM 1649 “Urban Dust”, to urban air samples from the city of Vienna as well as to combustion emissions.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 106 (1975), S. 19-26 
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In a previous paper1 it has been shown that C2H3O+ ions generated from different compounds isomerize to a common structure (or mixture of structures) prior to decomposition in the field-free region of the mass spectrometer. In the present work metastable transitions of12C13CH3O+ ions generated from acetone-2-13C are investigated, in order to find out if the isomerized structure is cyclic or linear. The results are in agreement only with a linear structure, about 8% of the ions showing migration of oxygen prior to decomposition. Isomerization to acetyl cation is assumed.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 106 (1975), S. 925-939 
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Abundance ratios of C2H4 and CO loss (CH4 and O loss) in the field-free region of a mass spectrometer have been determined by mass resolution of metastable peaks. Using the method ofShannon andMcLafferty the abundance ratios have been applied to characterize the structure of metastable ions. C3H5O+ ions from 10 compounds and C4H7O+ ions from 14 compounds have been examined. In the case of C3H5O+, three types of structurally different isomers are present. C4H7O+ ions represent a not equilibrating mixture of different. structures in some cases. From examination of 2-pentanone-1,1,1,3,3-d 5, metastable C4H7O+ ions from 2-pentanone have been shown to consist of two structurally distinct types of ions which are assumed to be $$\begin{array}{*{20}c} {CH_2 - O^ + } \\ {\begin{array}{*{20}c} | & {||} \\ \end{array} } \\ {CH_2 - C - CH_3 } \\ \end{array}$$ and butyryl ion.
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  • 9
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The mass spectrometric fragmentation behaviour of four monosubstituted pyridazines (phenyl-3- and phenyl-4-pyridazinylmethanol, phenyl-3-pyridazinyl and phenyl-4-pyridazinyl ketone) was investigated. Fragmentation pathways were established by combined interpretation of the data obtained from high resolution measurements and from low-energy collision-activated dissociation mass spectra of the molecular ions as well as of several important fragment ions. A clear differentiation between these 3- and 4-substituted 1,2-diazines is possible for both sets of pyridazines. Only the spectra of the 3-isomers exhibit an abundant [M—H]+ peak, which indicates a cyclization of these ions involving one ring nitrogen atom. Another difference between the two isomeric phenylpyridazinylmethanols is the loss of OH from the molecular ion, as detected for the C-3 substituted compound only. For the phenylpyridazinyl ketones, the loss of CO from the molecular ion, which is only observed with the 3-isomer, permits an unequivocal differentiation.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 7 (1993), S. 99-105 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: New methods are presented for the evaluation of ion structures and fragmentation pathways using tandem mass spectrometry (MS/MS) with low energy collision-induced dissociation. As an aid for mass spectroscopists, they incorporate a PC software package (named PDNL, written in Turbo-PASCAL 5.5 (Borland), running under DOS (Microsoft) with mouse-control). A database of almost 300 low energy MS/MS spetra is available for library searches. It utilizes a new, intensity-based matching algorithm fitting to the demand of MS/MS data. Computational methods have been developed for (i) the separation of the spectra of unresolved isobaric ions and evaluation of the ratio of the ion abundances, (ii) the evaluation of single-collision spectra using the multi-collisional data map, and (iii) the elucidation of collision-induced dissociation fragmentation pathways. Principal component analyses of sets of at least eight MS/MS spectra were used for a quick comparison of these spectra and for a summary of inter-ion relationships.
    Additional Material: 6 Ill.
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