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  • 1990-1994  (4)
  • 1985-1989  (4)
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  • 1
    Electronic Resource
    Electronic Resource
    On the use of laser microprobe mass spectrometry for the analysis of organic biomolecules (1989)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 18 (1989), S. 581-591 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Laser microprobe mass spectrometry has been applied to a variety of organic polyfunctional molecules, covering a wide range of polarity and mass spectrometric behaviour. The technique apparently combines desorption under relatively soft conditions with extensive fragmentation and hence allows much structural information from intactly released thermolabiles to be obtained. The mass spectra appear unfamiliar in comparison to conventional techniques. Interpretation is attempted in a purely empirical way by means of the evidence from our database and tentative hypotheses to rationalize the desorption and ionization by laser microbeam irradiation of organic solids. Selected examples are presented to illustrate the potential and limitations of the method in the field of biomolecules, such as pyridoxine and pyridoxal phosphate, nucleosides, nucleotides and related analogues, drugs and the corresponding N-oxides.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200180813
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    In-depth limitation of the Lamma 500 for the in situ localization of organic compounds in biological embedded tissue samples (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 16 (1988), S. 113-119 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The objective of this study was exploration of the potential, offered by the laser microprobe mass spectrometer (LAMMA), for the in situ localization of organic targets in embedded tissues by means of structurally relevant ions. A series of model systems was designed to evaluate stepwise the analytical problems involved. A preliminary screening pointed to the position of the target in comparison to the actual sample surface as a determining parameter. Refined simulations were carried out with sandwich samples, consisting of an epon carrier (thickness 1 μm), coated with microcrystalline targets and covered with a layer between 5 and 50 nm of different materials (epon, carbon, formvar). In addition to a stimulated conversion of molecular into fragment ions, the presence of a barrier leads to a drastic loss of sensitivity (20-50 x) and unacceptable degradation of the mass spectrometric quality (resolution, calibration).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200160120
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Structural characterization of drugs and oxygenated metabolites by laser microprobe mass spectrometry (LAMMA) (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 16 (1988), S. 121-129 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Laser microprobe mass analysis (LAMMA) was used for the structural characterization of polyfunctional drugs and their oxygenated metabolites, in particular the N-oxides. The spectra usually yield the molecular weight as well as intense fragments. The structural information is characteristically distributed between the positive and negative ions. To rationalize the unfamiliar fragmentation, tentative pathways are introduced. Key elements are the formation of odd-electron molecular (and fragment) ions, the correlation between cations and anions, as well as the three-dimensional representation of structures. The combination of mild desorption and abundant fragmentation makes LAMMA a valuable tool in the study of N-oxides.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200160121
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Analysis of X-ray spectra by iterative least squares (AXIL): New developmentsPresented at the European Conference on EDXRS, Budapest, Hungary, May 30-June 3, 1994 (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 23 (1994), S. 278-285 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The functionality of the computer package AXIL (Analysis of X-ray spectra by Iterative Least squares), suitable for the evaluation of energy-dispersive X-ray spectra, has been extended in a number of ways. First, a background modelling algorithm, based on the use of mutually orthogonal polynomials was introduced to replace the linear or exponential polynomials employed previously. Second, the Gaussian photopeak model employed in previous versions of the program was extended to include the non-Gaussian parts of the characteristic peaks and related background contributions. Both innovations are shown to improve the performance of the spectrum evaluation procedure. Third, the user-friendliness of the evaluation program was enhanced (a) by allowing a PC plug-in MCA card to be directly controlled from within the program and (b) by extending the command-interface to allow for repeated execution of series of commands by means of control loops. A brief description of these changes is given; as an application, the accurate evaluation of micro-XRF images is discussed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300230609
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Structural characterization of organic molecules by negative ions in laser microprobe mass spectrometry. Part 2 - Salts (1989)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 24 (1989), S. 797-806 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Laser microprobe mass spectrometry (LMMS) has been applied systematically to a variety of organic polyfunctional molecules, covering a wide range of structures and polarities. The microprobe generally offers a combination of desorption under relatively mild conditions with abundant fragmentation. We attempted an empirical approach by tentative hypotheses about desorption and ionization in LMMS to consistently rationalize the detected fragments. The complementary nature of structural data, carried by positive and negative ions, is characteristic for LMMS results of non-ionic compounds. The analysis of salts represents, traditionally, an ultimate test case for soft methods in organic mass spectrometry. Hence, by a selected series of compounds, we have tried to assess to which extent the presence of preformed ions becomes an asset for LMMS analysis and affects the amount, the accessibility or the distribution of organic information between positive and negative fragments.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210240913
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Determination of sample thickness via scattered radiation in x-ray fluorescence spectrometry with filtered continuum excitation (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 19 (1990), S. 29-33 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A semi-empirical approach is described for determining the mass per unit area of a sample being analysed. The method can be used to estimate the concentration of minor and trace elements in matrices containing a substantial amount of light elements. The procedure utilizes the coherently and incoherently scattered radiation induced in the sample by the filtered continuum radiation of a rhodium x-ray tube. The relationship between the intensity of the scattered radiation per unit mass and the average atomic number of the sample is established via calibration graphs, which can be applied for different x-ray tube voltages and for different primary beam filters. The overall procedure was validated by the analysis of several geological standards, deposited as thin slurries of unknown thickness either on Mylar foil or on Nuclepore filters.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300190107
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Monte Carlo simulation of conventional and synchrotron energy-dispersive x-ray spectrometersPresented at the European Conference on EDXRS, Myconos, Greece, 30 May-6 June 1992. (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 22 (1993), S. 234-243 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A number of examples of the use of a detailed Monte Carlo (MC) simulation program for EDXRF spectrometers is discussed. The MC code is employed to predict the complete spectral response of a polychromatic EDXRF spectrometer using different excitation conditions. With respect to quantification of steel samples in which significant enhancement and self-absorption occur, the usefulness of the code in simulating spectra corresponding to calibration standards is demonstrated. An extension of the program that deals with simulating the interaction of polarized radiation with matter is used to estimate the analytical qualities of currently operating and future mono-and polychromatic synchrotron radiation XRF spectrometers.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300220412
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Mα/Lα intensity ratios for Ta, W, Pt, Au, Pb and Bi for electron energies in the 11-40 keV range (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 22 (1993), S. 372-376 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Both energy- and wavelength-dispersive systems were used to obtain Mα/Lα intensity ratios for Ta, W, Pt, Au, Pb and Bi at various overvoltages. A table of these ratios corrected for matrix absorption and detector efficiency is presented, in addition to an interpolatory function of Mα/Lα generated ratios vs. overvoltage, for each element. In addition, three different ZAF correction models were used to predict both detected and generated ratios. Finally, experimental Mβ/Mα ratios measured at different overvoltages are presented for the six elements considered.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300220510
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    Paper (German National Licenses)
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