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  • Analytical Chemistry and Spectroscopy  (133)
  • Physics
  • 1995-1999  (133)
  • 1980-1984
  • 1965-1969
  • 1995  (133)
Sammlung
Verlag/Herausgeber
Erscheinungszeitraum
  • 1995-1999  (133)
  • 1980-1984
  • 1965-1969
Jahr
  • 1
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 712-716 
    ISSN: 0951-4198
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: A variety of ionophores have been studied by packed column supercritical-fluid chromatography combined with mass spectrometry. One of the ionophores, lasalocid, provided particularly good multiple-reaction monitoring signal-to-noise responses when analysed by tandem mass spectrometry and this approach shows considerable potential for the analysis of this compound in medicated animal feeds. A capillary supercritical-fluid chromatograph has been interfaced to an unmodified benchtop quadrupole mass spectrometer and this combination has enabled the molecular weight determination of the sodium salt of an ionophore.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 1 (1995), S. 291-296 
    ISSN: 1075-4261
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Physik
    Notizen: Deoxycholic acid is an important physiological bile acid. The binding of bile salts with metal ions has received more attention due to its clinical significance. In this study, a series of copper and zinc deoxycholate complexes were synthesized. EXAFS and FTIR spectroscopic techniques were used for characterization. The results indicated that both the carboxyl and hydroxyl groups of deoxycholic acid are binding to the Cu (or Zn) ion to form a new complex. There are six oxygen atoms surrounding the metal ion with the average bond lengths of Cu-O and Zn-O are 1.95 and 2.06 Å respectively. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    ISSN: 0749-1581
    Schlagwort(e): non-empirical calculations ; NQR parameters ; Townes and Dailey theory ; three-membered rings ; LMO approach ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The nuclear and electronic contributions to the EFG tensor components eqii at 14N, 17O, 33S and 35Cl nuclei in aziridine, methylaziridine, chloroaziridine, oxirane and thiirane were determined. The nuclear contributions were calculated within classical representations, while electronic contributions were calculated non-empirically using a 6-31G* basis set within the framework of the LMO approach. On the basis of the analysis of the contributions to the EFG tensor components from definite bond and lone-pair orbitals, the main concepts of the Townes and Dailey approach were tested.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 1 (1995), S. 149-156 
    ISSN: 1075-4261
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Physik
    Notizen: A series of copper bilirubinate complexes (CuBR) was synthesized in solution and in solid state to mimic the black color of the black-pigment gallstone and to explore the formation mechanism of the gallstonein vitro. The variation of the copper contents of these samples indicated that CuBR also exhibits nonstoichiometric characteristics from the FTIR study, i.e., both the so-called acid and neutral copper complex moieties exist in CuBR. The NH groups in pyrrole and lactam groups of bilirubin (H2BR) are binding to the copper ions. An EPR study demonstrates the generation of free radicals and the variation of its electronic structure and conjugation system in the skeleton of H2BR molecule during complex formation. A polymer of CuBR may form through the reaction of H2BR with copper ions. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    ISSN: 1076-5174
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Tandem mass spectrometric methods for the identification of 19-norandrosterone (3α-hydroxy-5α-estran-17-one) are described and evaluated. The fragmentation reactions of the heptafluorobutyryl (HFB) and pentafluorobenzyloxime heptafluorobutyryl (PFBO—HFB) ester derivatives of 19-norandrosterone (3α-hydroxy-5α-estran-17-one) in particular were studied for the purpose to select characteristic ions. The HFB ester was analyzed by collisionly activated dissociation (CAD) following electron impact in order to fragment the steroid nucleus. The formation of D-ring fragments, i.e. the ring containing the keto function, was typical for this type of derivative. Cleavages of fragments with an intact D-ring were also prominent. The PFBO—HFB ester was formed to create a derivative, which could capture electrons and be analyzed in the Electron Capture Negative Chemical Ionization (ECNCI) mode. Besides fragmentations originating in the groups coupled to the steroid by derivatization, also characteristic D-ring fragments were observed by CAD following ECNCI. Accordingly, of both methods evaluated only CAD following EI of the HFB derivative of 19-norandrosterone provided a characteristic MS/MS procedure for the identification of 19-norandrosterone under the conditions studied.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    ISSN: 1076-5174
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Tandem mass spectrometric methods for the identification of 19-nortestosterone (estr-4-en-17β-3-one) are described and evaluated. The fragmentation reactions of the heptafluorobutyryl (HFB) and pentafluorobenzyloxime heptafluorobutyryl (PFBO—HFB) ester derivatives of 19-nortestosterone in particular were studied for the purpose to select characteristic ions. The HFB ester was analyzed by collisionly activated dissociation (CAD) following electron impact in order to fragment the steroid nucleus. Cleavage of the A-ring, i.e. the ring containing the keto function, was prominent. The formation of A-, A/B- and D-ring fragments was also typical for this type of derivative. The PFBO—HFB ester was formed to create a derivative, which could capture electrons and be analyzed in the electron-capture negative chemical ionization (ECNCI) mode. Besides fragmentations originating in the groups coupled to the steroid by derivatization, no prominent steroid nucleus fragmentations were observed by CAD following ECNCI. Accordingly, of both methods only CAD following EI of the HFB derivative of 19-nortestosterone provided a characteristic MS/MS procedure for the identification of 19-nortestosterone.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 114-118 
    ISSN: 0951-4198
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: Dissociation of C60- ions induced in 30 keV collisions with atomic and molecular gases has been studied. The pattern of negativeion formation from C60- precursors is found to be distinctly different from that obtained for positive-ion fragments from C60+ precursors in that the collision-induced dissociation spectrum in the former case is dominated by small negative clusters, presumably of linear geometry, Simple arguments utilizing the relationship of electrostatic properties of different molecular structures to their electron affinities and ionization energies have been invoked to rationalize these observations. The difference in the dissociation dynamics of C60- and C60+ ions is discussed in terms of competition between different energy-coupling schemes involving either electronic degrees of freedom or nuclear (vibrational) degrees of freedom.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 1376-1379 
    ISSN: 0951-4198
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: The mass spectrometric behaviour of two pairs of fluorinated vinyl- and allyl-ethers and thioethers has been studied in detail with the aid of metastable ion data and accurate mass measurements. Clear differences have been observed between the two sets of compounds; while for the ethers the McLafferty rearrangement with ethylene loss represents a highly favoured decomposition route, for the thioethers the loss of the ethyl radical is preferred. Some decomposition routes, common to all the compounds examined, suggest the presence of hydrogen atom bridging between carbon and fluorine atoms. Theoretical calculations have shown that such a quasi C—H—F structure is already present in the neutral molecule in its ground state.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    ISSN: 0951-4198
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: The electron-ionization induced mass spectra of some N-monosubstituted fluoroacetamides of the general formula FCH2—CONH—R, in which the substituent R is (C3—C7) cycloalkyl, phenyl, 4-methylphenyl, 4-carbo-methoxyphenyl, 4-nitrophenyl and 4-diethylaminophenyl, were recorded and their fragmentation patterns were studied by metastable-ion analyses.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    ISSN: 1076-5174
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A mass fragmentographic method for the measurement in plasma of underivatized, dehydrated 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3 was developed. Quantitative dehydration of vitamin D metabolites was achieved prior to gas chromatography using a new high-temperature injection system and a small precolumn packed with aluminium powder in the injection port, followed by mass fragmentography on an inexpensive bench-top mass spectrometer. Plasma (2 ml) was incubated with hexadeuteriated 25-hydroxyvitamin D3 prior to acetonitrile extraction and purification using cartridges pre-packed with microparticulate silica using reversed- and normal-phase solvent systems. After purification, capillary gas chromatography mass spectrometry was carried out following dehydration of the secosteroids on the aluminium power pre-column at 400°C. High-intensity dehydrated molecular ions were produced which were used for selected ion monitoring. The assay sensitivity for 25-hydroxyvitamin D was approximately 1 ng ml-1. The intra-assay variation was less than 7% and the recovery of added standard was quantitative. It is suggested that this method may be used to provide target values for much needed quality control schemes to monitor assays routinely used in the estimation of 25-hydroxyvitamin D. The behaviour of a number of other hydroxylated vitamin D metabolites, when injected without derivatization on to a gas chromatographic column, was also investigated.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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