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  • Digitale Medien  (90)
  • Analytical Chemistry and Spectroscopy  (48)
  • General Chemistry  (42)
  • 1
    Digitale Medien
    Digitale Medien
    Rapid identification of drug metabolites with tandem mass spectrometry (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 193-204 
    Details
    ISSN: 0887-6134
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A method which involves the use of tandem mass spectrometry (MS/MS) for the identification of drug metabolites has been demonstrated with a triple quadrupole mass spectrometer. The method is based on the fact that metabolites usually retain various substructures of the original drug molecule. MS/MS is capable of rapidly identifying molecules with characteristic substructures without prior separation. It is shown that this method makes it possible to postulate possible drug metabolite structures rapidly and systematically without the use of standards. The MS/MS method, as it was applied to the identification of the metabolites of a new antiepileptic drug, zonisamide, is discussed. In this case it was possible to identify isomeric metabolites due to their differences in vaporization times off the probe and their different daughter spectra. The complementary uses of the neutral loss and parent scans for the determination of the site of metabolism is demonstrated. A new figure of merit, the limit of identification, is introduced. The amount of the epoxide metabolite of carbamazepine necessary for its reliable identification in urine was shown to be 0.4 ng/μl. The application of various techniques to confirm preliminary findings with this MS/MS method are described.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bms.1200150403
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  • 2
    Digitale Medien
    Digitale Medien
    Determination of cyclopentolate by capillary column gas-liquid chromatography (1984)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 7 (1984), S. 144-146 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Capillary column ; Cyclopentolate ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240070310
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  • 3
    Digitale Medien
    Digitale Medien
    A convenient computer program for calculation of Kováts retention indexes (1992)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 15 (1992), S. 478-479 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Kováts retention index ; GW-BASIC program ; Computer-assisted calculation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240150714
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  • 4
    Digitale Medien
    Digitale Medien
    A novel algorithm for chromatogram matching in qualitative analysis (1992)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 15 (1992), S. 539-547 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Neural networks ; Pattern recognition ; Simulated data ; Simulated annealing ; Essential oils ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The matching of the pattern of peaks produced during gas chromatography is of importance to many applications. At present, this task is generally performed manually, but this generates the usual problems associated with human inspection, such as a lack of objectivity and reproducibility, proneness to errors, and practical restriction of the volume of data which can reasonably be processed.This paper explores the use of a novel algorithm for automation of this task. The performance of the method on well controlled simulated data sets and real chromatograms is used to show not only how problems of manual inspection can be circumvented, but also how the existence of such a powerful method should open up the possibility of many new analyses for quality control, discrimination of varieties of sample, and the identification of specific components within a sample.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240150811
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  • 5
    Digitale Medien
    Digitale Medien
    Letter to the editor (1993)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 52-52 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240160110
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  • 6
    Digitale Medien
    Digitale Medien
    Direct database searching with MALDI-PSD spectra of peptides (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 1546-1551 
    Details
    ISSN: 0951-4198
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: The analysis of matrix-assisted laser desorption ionization post-source decay (MALDI-PSD) mass spectra of peptides by using the cross-correlation method for database searching is illustrated. MALDI-PSD mass spectra are shown to contain sufficient fragmentation information to uniquely identify the correct amino acid sequence from large protein databases (∼160000 entries). A search employing the MALDI-PSD mass spectrum of a phosphorylated peptide that correctly identifies the amino acid sequence and the site of phosphorylation is also illustrated.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/rcm.1290091515
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  • 7
    Digitale Medien
    Digitale Medien
    Analysis of inositol mono- and polyphosphates by gas chromatography/mass spectrometry and fast atom bombardment (1986)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 13 (1986), S. 333-341 
    Details
    ISSN: 1052-9306
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The electron ionization spectra of all of the positional isomers of myo-inositol monophosphate and of myo-inositol 1,2-cyclic phosphate were obtained by gas chromatography/mass spectrometry of the pertrimethylsilyl derivatives. The fragmentation pattern of pertrimethylsilyl myo-inositol-1-phosphate was studied using deuterium labeling. The phosphate moiety was found to direct fragmentation to produce fragment ions of useful intensity with specific carbon retention. The spectrum of pertrimethylsilyl myo-inositol-1,4-bisphosphate is also described. An electron impact gas chromatographic/mass spectrometric method for myo-inositol-1-phosphate has been developed, which has a sensitivity to a level of 0.1 pmol. The positive and negative ion fast atom bombardment spectra of myo-inositol hexakis(disodium phosphate) and myo-inositol hexakis(dihydrogen phosphate) are described. The lesser-phosphorylated inositol polyphosphates were also studied, including inositol pentakis and inositol tetrakis(dihydrogen phosphates) as well as D-myo-inositol-1,4,5-trisphosphate and D-myo-inositol-1,4-bisphosphate from human red blood cells. The sensitivity of fast atom bombardment for the measurement of the latter two substances allows their detection to a level of about 10 nmol. The fast atom bombardment spectrum of synthetic myo-inositol 1,2-cyclic phosphate revealed variable amounts of a dimer produced during its preparation.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bms.1200130704
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  • 8
    Digitale Medien
    Digitale Medien
    Optimization of short-column gas chromatography/electron ionization mass spectrometry conditions for the determination of underivatized anabolic steroids (1992)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 21 (1992), S. 420-430 
    Details
    ISSN: 1052-9306
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A gas chromatographic/mass spectrometric method based on the use of short capillary gas chromatograph columns (3-5 m) and electron ionization mass spectrometry has been optimized and evaluated for the determination of underivatized anabolic steroids. The short-column gas chromatographic/mass spectrometric method was shown to result in short analysis times and to require minimal sample preparation, but suffered from some loss in sensitivity and chromatographic resolution compared with conventional gas chromatographic/mass spectrometric techniques for derivatized steroids. Therefore, short-column gas chromatographic conditions were optimized to maximize the sample transfer efficiency (sensitivity) from the gas chromatograph into the ion source of the mass spectrometer, while maintaining chromatographic integrity and minimizing thermal decomposition. Mass spectrometric conditions were optimized to maximize ionization efficiency with respect to the intensity of the molcular ion and degree of fragmentation such that positive identication of each steroid could be made based on the resulting mass spectra. Under optimized conditons, we have shown that underivatized anabolic steroids spiked into urine samples can be determined at low-nanogram levels using short-column chromatography/full-scan electron ionization mass spectrometry.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bms.1200210903
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  • 9
    Digitale Medien
    Digitale Medien
    The stretched quadrupole ion trap: Implications for the Mathieu au and qu parameters and experimental mapping of the stability diagram (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 760-764 
    Details
    ISSN: 0951-4198
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: The effect of the radial and axial dimensions on the Mathieu stability diagram (in terms of DC and RF voltages) is discussed with relation to the ‘stretched’ geometry employed in the Finningan MAT quardrupole ion-trap mass spectrometer (ITMS). Equations are presented for the conversion of the Mathieu au and qu parameters to DC voltages and RF voltages, respectively, and vice versa on the ITMS. A TURBOBASIC program is discussed which will provide data for graphing of a stability diagram in (RF, DC) space. Experimentally determined boundaries of the stability diagram are in good agreement with an approximate model for the stretched trap.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/rcm.1290061210
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  • 10
    Digitale Medien
    Digitale Medien
    Black canyons for ions stored in an ion-trap mass spectrometer (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 573-578 
    Details
    ISSN: 0951-4198
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: Effects from higher order non-linear resonances, ‘black canyons’, have been observed for ions stored within the quadrupole ion-trap mass spectrometer. At specific qz values, higher-order field effects were observed to cause decreased intensity of chemical ionization (CI) reagent ions, due to ineffcient storage, as well as collision-induced dissociation. Efects have been observed, whether or not the CI reagent ions are mass-selected, and exibit increased severity with longer storage times. Previous reports have shown ‘black holes’ due to inefficient storage of product ions in tandem (MS/MS) spectra, but have reported no such effects in normal mass spectra. Without employing resonant excitation, higher-order field effects were investigated and found to occur continuously along iso-βz lines for βz = 1/3, 1/2, and 2/3. Described in this paper are the directs from higher-order fields on ions stored at specific az values, and indirec effects by those ions. Also described in this paper is new evidence for ‘black canyons’ occurring at βz = 1/3 at negative az values.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/rcm.1290060908
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