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  • 1
    Electronic Resource
    Electronic Resource
    Force-field andab initio calculations of five-membered rings: I. Symmetry coordinates for molecules with nonideal pentagonal geometry (1983)
    Springer
    Journal of chemical crystallography 13 (1983), S. 135-141 
    Details
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A mathematical description for the symmetry coordinates of the vibrational fundamentals of five-membered ring systems is presented. A force-constant calculation was performed for 1,3-dioxol-2-one and compared with results assuming an ideal pentagon. Though the deviation of the ring fromD 5h , symmetry is rather small, some force constants already show differences in the first digit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01246582
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  • 2
    Electronic Resource
    Electronic Resource
    Force-field andab initio calculations of five-membered rings: II. Force constants and ab initio gradient calculations of the geometries of dioxoles and dithioles (1983)
    Springer
    Journal of chemical crystallography 13 (1983), S. 143-150 
    Details
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Ab initio gradient calculations of the geometries of 1,3-dioxol-2-one, -thione, -onium, and the analogous 1,3-dithioles are reported. Together with force constants derived from GVFF calculations, these results give evidence of the changes in structure when substituting oxygen by sulfur. The electronic structure as well as the vibrational behavior are mainly determined by the electronic delocalization of the heteroatoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01246583
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  • 3
    Electronic Resource
    Electronic Resource
    Reversed-phase ion-pair chromatographic separation of selenite and selenate with selenium-specific detection (1995)
    Springer
    Microchimica acta 119 (1995), S. 113-127 
    Details
    ISSN: 1436-5073
    Keywords: reversed-phase ion-pair chromatography ; selenium-specific detection ; selenite ; selenate ; selenium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Tetraalkylammonium salts [R3R′N]+X− (R=R′, X∶CH3, Cl; C2H5, Br; C3H7, Br; C4H9, H2PO4; C5H11 Br; R, R′, X∶CH3, C16H33, Br) were investigated as ion-pairing reagents for the reversed-phase ion-pair chromatographic separation of selenite and selenate. Other chromatographic parameters such as composition and pH of the mobile phase and concentration of the ion-pairing reagent were also investigated. The compatibility of the proposed chromatographic procedures with various selenium-specific detectors is discussed. The absolute detection limits were found to be 31 ng Se for selenite and 51 ng Se for selenate (100 μl injection) with a solution of 5 mM tetrabutylammonium dihydrogen phosphate in 50∶50 (v/v) methanol/water as mobile phase at a flow rate of 1 ml/min when a flame atomic absorption spectrometer was used as detector. The HPLC/FAAS system was employed for the determination of selenite in solutions serving as selenium supplement for animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01244860
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  • 4
    Electronic Resource
    Electronic Resource
    Stripping voltammetric determination of trace amounts of mercury using a carbon paste electrode modified with 2-mercapto-4(3H)-quinazolinone (1993)
    Springer
    Microchimica acta 112 (1993), S. 135-146 
    Details
    ISSN: 1436-5073
    Keywords: stripping voltammetry ; mercury ; carbon paste electrode ; 2-mercapto-4(3H)-quinazolinone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A carbon paste electrode modified with 2-mercapto-4(3H)-quinazolinone was used for the voltammetric determination of mercury(II). Mercury was preconcentrated onto the surface of the modified electrode only by the complexing effect of the modifier without application of potential (i.e. in open-circuit conditions). After exchange of the medium, the accumulated amount of mercury(II) was determined by differential pulse anodic stripping voltammetry. The response depended on the concentration of mercury in the bulk solution, preconcentration time, and other parameters. The detection limit was 0.1 μg 1–1 Hg(II) for a preconcentration time of 15 min. Preconcentration for suitable times yielded a linear calibration graph from 0.5 to 6000 μg 1–1 Hg(II). For multiple determinations (5 runs), the relative standard deviation was 5% for a concentration of 100 μg 1–1 Hg(II). The proposed procedure was used to determine trace mercury in plant and sewage sludge samples with good results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01243330
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  • 5
    Electronic Resource
    Electronic Resource
    Ab-initio-Berechnungen des π-Bindungsbeitrages in BF3 und BCl3 (1981)
    Springer
    Monatshefte für Chemie 112 (1981), S. 1123-1128 
    Details
    ISSN: 1434-4475
    Keywords: Ab initio ; π-Bonding ; Boronchloride ; Boronfluoride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ab initio gradient calculations were performed on BF3 and BCl3 to evaluate the π-contribution in these compounds. The influence of the basis set on the results is studied for borontrifluoride. For the chlorine compound the π-contribution is smaller than for the fluorine compound.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00905466
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  • 6
    Electronic Resource
    Electronic Resource
    Kraftfeld- und CNDO-Rechnungen von Vanadium-N-chlorimid-trichlorid CINVCL3 (1981)
    Springer
    Monatshefte für Chemie 112 (1981), S. 917-924 
    Details
    ISSN: 1434-4475
    Keywords: N-Chlorimido-vanadium(V) trichloride ; Force Constants ; CNDO calculations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Force field and CNDO calculations were performed on CINVCl3. These results give some evidence for the large CINV bond angle and the short CIN distance. One can conclude that for the CIN bond a large π contribution must be assumed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00905063
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  • 7
    Electronic Resource
    Electronic Resource
    π-Bindungsbeitrag in Boranen, 2. Mitt.:Ab initio- und Kraftfeld-Rechnungen von Vinyldifluorboran (1982)
    Springer
    Monatshefte für Chemie 113 (1982), S. 265-273 
    Details
    ISSN: 1434-4475
    Keywords: Ab initio ; π-Bond ; Force field ; Rotational barrier ; Vinyldifluoroborane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ab initio calculations on vinyldifluoroborane yield a π-contribution of 23 kJ/mol (5.5 kcal/mol) mainly due to the C=C bond and not to the lone pairs of the fluorine atoms. The rotational barrier was also determined. The force field calculations favour the interpretation of the bond structure derived from the theab initio results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00799553
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  • 8
    Electronic Resource
    Electronic Resource
    A compact electrode assembly for voltammetric measurements with solid electrodes (1986)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 323 (1986), S. 238-240 
    Details
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Summary An electrode assembly is presented consisting of a cell compartment of plexiglass and an electronic circuit for automatic performance. It was especially designed for the use with polarographs PAR 264, 264 A, 384 and 384 B when working with solid electrodes. A special attempt was made to reduce the metallic parts of the assembly to a minimum in order to avoid contamination risks when analyzing heavy metals.
    Notes: Zusammenfassung Ein Elektrodenstand wird beschrieben, der aus einer Meßzelleneinheit aus Plexiglas und einem elektronischen Schaltkreis für automatischen Betrieb besteht. Er wurde speziell für die Polarographen-PAR-Modelle 264 und 384 für voltammetrische Messungen mit Festkörperelektroden konzipiert. Um bei Schwermetallanalysen das Kontaminationsrisiko möglichst gering zu halten, wurden metallische Teile der Zelle weitgehendst vermieden.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00464081
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  • 9
    Electronic Resource
    Electronic Resource
    Voltammetrische Bestimmung von Iodid mit einer mit Anionenaustauschern modifizierten Kohlepasteelektrode (1985)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 321 (1985), S. 666-670 
    Details
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Das elektrochemische Verhalten von Iodid an mit Anionenaustauschharzen modifizierten Kohlenpasteelektroden wird untersucht. Die Ionen können stromlos nur durch die Ionenaustauschwirkung der Elektrode vorkonzentriert werden. Nach Mediumswechsel kann die angereicherte Menge lodid, die von der Konzentration in der Lösung abhängig ist, entweder durch kathodische oder anodische differentielle Pulsvoltammetrie bestimmt werden. Viele Faktoren wie Zusammensetzung der Paste, pH-Wert u.s.w. beeinflussen das elektrochemische Signal. Für Iodid konnte eine gute Linearität zwischen Konzentration und Peakstrom für den Bereich 5–80 ppm gefunden werden.
    Notes: Summary The electrochemical behaviour of iodide on carbon paste electrodes modified by addition of anion-exchange resins is investigated. The ions can be preconcentrated without application of a potential only by the ion-exchange effect of the modified electrode. After medium exchange the accummulated amount of iodide, which depends on the bulk concentration, can be determined by either cathodic or anodic differential pulse voltammetry. Many parameters like composition of the paste, pH etc. influence the response of the measurement. Good linearity between concentration and peak current is found for iodide in the range between 5 and 80 ppm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00489632
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  • 10
    Electronic Resource
    Electronic Resource
    Voltammetrisches Verhalten von Hexachloroiridat(IV)-lösungen an chemisch modifizierten Kohlepasteelektroden (1986)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 324 (1986), S. 47-52 
    Details
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Hexachloroiridat(IV)-lösungen können mittels einer chemisch modifizierten Kohlepasteelektrode analysiert werden. Die Modifizierung geschieht durch einen schwach basischen Flüssigionenaustauscher. Die Iridationen können stromlos an der Elektrodenoberfläche angereichert werden. Die Parameter, die die Signalhöhe beeinflussen, sowie die Beziehungen zwischen Konzentration, Anreicherungszeit und Peakstrom werden untersucht. Die Methode eignet sich für Iridiumkonzentrationen über 0,2 ppm.
    Notes: Summary Hexachloroiridate(IV) solutions can be analyzed by differential pulse voltammetry using a chemically modified carbon paste electrode. The modifying agent is a liquid anion-exchanger with secondary amine functional groups. Thus, iridate ions can be preconcentrated on the electrode surface without application of a potential. The parameters influencing the signal response, and the relations between concentration, accumulation time and peak current are investigated. The method is suitable for Ir concentrations higher than 0.2 ppm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00469633
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