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  • Inorganic Chemistry  (18)
  • Computational Chemistry and Molecular Modeling  (6)
  • Solid-phase extraction  (4)
  • 42.75
  • 1995-1999  (23)
  • 1960-1964  (6)
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  • 1
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Atomic emission and MS detection ; Solid-phase extraction ; Aqueous samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A procedure is described for the (non-target) screening of hetero-atom-containing compounds in tap and waste water by correlating data obtained by gas chromatography (GC) using atomic emission (AED) and mass selective (MS) detection. Solid-phase extraction (SPE) was coupled on-line to both GC systems to enable the determination of microcontaminants at the 0.02–1 μg L−1 level in 7–50 mL of aqueous sample. The screening was limited to compounds present in at least one heteroatom-selective GC-AED trace above a predetermined concentration level. These compounds were identified by their partial formulae (AED) and the corresponding mass spectra, which were obtained from the GC-MS chromatogram via the retention index concept. The potential of the approach was demonstrated by the identification of target compounds as well as all unknowns present in tap and waste water above the predetermined threshold of 0.05 μg L−1 (tap water) or 0.5 μg L−1 (waste water).
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  • 2
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Atomic emission detection ; Aqueous samples ; Solid-phase extraction ; Organophosphorus pesticides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An on-line, solid-phase extraction gas chromatography atomic-emission detection (SPE-GC-AED) system has been set up using an on-column interface to transfer 100 μl of desorbing solvent to the GC part of the system. Analytical characteristics such as recovery, precision and linearity of calibration plots were comparable with those of the off-line combination of SPE-GC-AED using organophosphorus pesticides as test compounds. The fully on-line set-up causes a marked improvement in detection because of the quantitative transfer of the analytes from the SPE module to the GC: detection limits are as low as 5–20 ng l−1 for the analysis of 10 ml raw and spiked surface water samples using the phosphorus channel. Detection levels can be further enhanced by processing up to 100 ml samples. The integrated analytical system is robust. The potential of the on-line set up has been demonstrated for the analysis of surface water and waste water.
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  • 3
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    In:  Nederlandse Faunistische Mededelingen (01692453) vol.9 (1999) p.109
    Publication Date: 2007-01-10
    Description: The rearing of the botfly Cephenemyia auribarbis (Diptera: Oestridae) After several failures we finally succeeded in rearing botflies Cephenemyia from third-instar larvae. From a red deer shot at 13 March 1998 about one hundred larvae of Cephenemyia auribarbis (Meigen, 1824) were collected. Ten individuals reached the pupal stage. After 22 days, one fullgrown male died in the pupa, and two males emerged and lived for 17 and 18 days respectively. This is one of the few recorded succesful attempts to rear botflies.
    Keywords: Insecta ; Diptera ; Oestridae ; Cephenemyia auribarbis ; Nederland ; Verspreiding ; 42.75
    Repository Name: National Museum of Natural History, Netherlands
    Type: Article / Letter to the editor
    Format: application/pdf
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  • 4
    ISSN: 1612-1112
    Keywords: Solid-phase extraction ; Gas chromatography ; Ion trap tandem mass spectrometry ; Water samples ; Environmental analysis ; Pesticides ; Bromide ; Nitrite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary On-line solid-phase extraction-gas chromatographyion-trap tandem mass spectrometry (SPE-GC-MS/MS) has been used for the trace-level determination of polar and apolar pesticides. The SPE-GC interface, an Autoloop 2000, was operated at an injection temperature of 90°C which permitted the determination of thermolabile pesticides such as carbofuran and carbaryl. Rectilinear calibration curves were obtained for the analytes tested over a range of 0.1–500 ng L−1, using a sample volume of 10–100 mL for enrichment on an SPE cartridge packed with styrene-divinylbenzene copolymer. The detection limits for the pesticides were in the 0.01–4 ng L−1 range. For a number of pesticides acceptable tandem mass spectra were obtained at levels as low as 0.1 ng L−1 level in real-life water samples. As a demonstration of the applicability of this technique for inorganic anions, bromide and nitrite were converted into 4-bromoacetanilide and 2-phenylphenol, respectively. The reaction products were pooled and subjected to simultaneous analysis by the present method using full-scan mass spectrometric detection. The detection limits were 0.3 and 2 ng L−1, respectively.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 56 (1995), S. 523-531 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dielectric constant of a material is a macroscopic property that measures the reduction of the electrostatic forces between charged plates separated by the material, compared to a vacuum as intermediate material. It is next encountered as a scaling parameter in Coulomb's law for interacting charges, not only in the force, but also in the energy. In deriving the theory for dielectrics, the macroscopic nature is essential: Only then is the basic assumption that the dielectric material is homogeneous and isotropic a valid one. The appearance of the dielectric constant as a simple scaling factor in Coulomb's law has tempted many computational chemists to forget about the macroscopic nature of the dielectric and to apply the screened Coulomb's law between charges, supposedly in a low-dielectric medium such as proteins, in microscopic force fields. Optimization of force fields even led to distance-dependent “dielectric constants.” Another use of the dielectric constant appears in the dielectric continuum reaction field approaches for the computations of solvation energies and solvent effects. The solute is embedded in a cavity surrounded by the dielectric. Specific interactions between solvent molecules and solute are thus neglected. The cavity size and dielectric constants of interior and exterior are optimized for the model. The aim of this article is to show, by means of calculations on interacting point charges embedded in cavities surrounded by dielectrics and microscopic models of “low-dielectric” materials by explicit polarizabilities, that as far as the dielectric “constant” is concerned anything can happen, depending on the nature of the charges, the distance to the cavity boundary, the spatial arrangement of charges, and polarizabilities. Thus, a warning is issued to injudicious use of dielectric models in microscopic calculations. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 57 (1996), S. 1067-1076 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solvent shift of the π* ← n transition of acetone in water, acetonitrile, and tetrachloromethane was calculated in a combined quantum mechanical - classical mechanical approach, using both dielectric continuum and explicit, polarizable molecular solvent models. The explicit modeling of solvent polarizability allows for a separate analysis of electrostatic, induction, and dispersion contributions to the shifts. The calculations confirm the qualitative theories about the mechanisms behind the blue shift in polar solvents and the red shift in nonpolar solvents, the solvation of the ground state due to electrostatic interactions being preferential in the former, and favorable dispersion interaction with the excited state, in the latter case. Good quantitative agreement for the solvent shift between experiment (+1,700, +400, and -350 cm-1 in water, acetonitrile, and tetrachloromethane, respectively) and the explicit solvent model (+1,821, +922, and -381 cm-1) was reached through a modest Monte Carlo sampling of the solvent degrees of freedom. A consistent treatment of the solvent could only be realized in the molecular solvent model. The dielectric-only model needs reparameterization for each solvent. © 1996 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 58 (1996), S. 185-192 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A simplified LCAO-DFT-LDA scheme for calculations of structure and electronic structure of large molecules, clusters, and solids is presented. Forces on the atoms are calculated in a semiempirical way considering the electronic states. The small computational effort of this treatment allows one to perform molecular dynamics (MD) simulations of molecules and clusters up to a few hundred atoms as well as corresponding simulations of condensed systems within the Born-Oppenheimer approximation. The accuracy of the method is illustrated by the results of calculations for a series of small molecules and clusters. © 1996 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 318 (1962), S. 190-197 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: (H2N-SO2-NH)Na and SO2Cl2 react in cold anhydrous acetonitrile yielding mainly O2S(NH-SO2-NH2)2 (I) and, to a small extent, (O2S-NH)4 (II). Both strongly hygroscopic compounds could not yet be obtained in the pure state. They are readily soluble in water, ethanol, and ether, though the solubility of II in ether is limited.The preparations and properties of the K-, Ba-, and Ag-salt of I are described. Methylation of I by means of diazomethane yields the very stable O2S[N(CH3)-SO2-N(CH3)2]2; its molecular weight confirms the formula given.By interaction of the starting compounds in boiling acetonitrile, the yield of (O2S-NH)4 increases; its Ba- and Ag-salt are characterized.
    Notes: Sulfamid-Natrium und Sulfurylchlorid reagieren in kaltem Acetonitril bei Wasserausschluß bevorzugt nach 2 H2N-SO2-NH-Na + Cl2SO2 → O2S(NH-SO2-NH2)2 + 2 NaCl. Daneben vollzieht sich in geringen Umfange, besser in der Siedehitze 2 H2N-SO2-NH-Na + 2 Cl2SO2 → (O2S-NH)4 + 2 NaCl + 2 HCl. Beide stark hygroskopischen Verbindungen wurden noch nicht rein erhalten, die 7gliedrige Verbindung ist neben anderen Solventien gut in Wasser, Äthanol und Äther, das wasserfreie (O2S-NH)4 gut in Wasser und Alkohol, weniger gut in Äther löslich.Das reine in Wasser mit neutraler Reaktion gut lösliche K-Salz, O2S(NK-SO2-NH2)2, liefert beim trockenen Erhitzen Trisulfimid, (O2S-NK)3, auch beim Erhitzen mit KOH, wobei aber NH3 abgespalten wird. Weiter wurde das in Wasser lösliche O2S(N-SO2-NH2)2 · Ba, 2 H2O und das darin unlösliche O2S(NAg-SO2-NH2)2 erzeugt. Bei tagelanger Einwirkung von ätherischer Diazomethan-Lösung auf eine ebensolche von rohem Sulfuryl-Disulfamid läßt sich das sehr beständige, bei 161° schmelzende O2S[N(CH3)-SO2-N(CH3)2]2 mit dem der Formel entsprechenden Molekulargewicht isolieren.Läßt man die O2SCl2-Umsetzung in siedendem Acetonitril sich vollziehen, so entsteht neben Trisulfimid mehr Tetrasulfimid. Das in kaltem Wasser schwerlösliche Ba2(NSO2)4, 2 H2O ließ sich gewinnen, ebenso das unlösliche (AgNSO2)4, dessen Debyeogramm mit dem in heißem Wasser löslichen (AgNSC2)3 aufgenommen und verglichen wurde.
    Additional Material: 1 Tab.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 324 (1963), S. 297-303 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: H2N—SO2—NH—Na reacts with Cl—SO3H or Cl/SO2—OC2H5 in boiling anhydrous nitromethane or acetonitrile yielding about 70—80% H2N—SO2—N(Na)—SO3Na(I).By means of I, the unknown (H2N—SO2—N—SO3)Ba, 2 H2O and (H2N—SO2—N—SO3)3- [Co(NH3)6]2 → 2H2O are obtained and their properties described.By interaction of H2N—SO2—NH—Na with Cl—SO2—OC2H5 at room temperature, 65% of H2N—SO2—N(Na)—SO2—OC2H5 were isolated. The hydrolysis with water or hydrochloric acid yields O2S(NH2)2 and C2H5O—SO3Na, that with ethanolic NaOH, however, I.
    Notes: Überschüssiges Na-Sulfamid reagiert mit Chloroschwefelsäure sowie deren Äthylester in siedendem Nitromethan oder Acetonitril bei völligem Feuchtigkeitsausschluß nach bzw. zu 70—80% unter Bildung von Na-Sulfamid-Monosulfonat.Das reine, mit stark alkalischer Reaktion in Wasser leichtlösliche Na-Salz H2N—SO2—N(Na)—SO3Na bildet ein Monohydrat. Es wurde zu den noch unbekannten Verbindungen (H2N—SO2—N—SO3)Ba, 2 H2O und (H2N—SO2—N—SO3)3 [Co(NH3)6]2, 2 H2O umgesetzt.Bei der Reaktion von Sulfamid-Natrium mit Cl—SO2—OC2H5 in Acetonitril bei Raumtemperatur entsteht mit 65% Ausbeute das Na-Salz des Sulfamid-Monosulfosäure-Äthylesters: das sich mit alkoholischer KOH zu H2N—SO2—N(Na)—SO3Na, hingegen mit Wasser oder 2 n HCl zu Sulfamid und Na-Äthylsulfat verseifen läßt.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 330 (1964), S. 164-169 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: A preparation method for high-melting crystalline metal oxides using thermally instable metal compounds which are decomposed in a fused alkali salt is described. Details of several decomposition reactions are briefly discussed.
    Notes: Es wird eine Darstellungsmöglichkeit für hochshmelzende kristalline Metalloxide durch thermischen Zerfall bei höherer Temperature instabiler Verbindungen beschrieben. Die Zersctzunggsreaktionen spielen sich hierbei in einer zweikomponentigen schmelzfüssigen Lösung ab, die aus der instabilen Verbindung und eimen Alkalisalz. Auf Einzelheiten des Reaktionsablaufs wird eingegangen.
    Additional Material: 3 Ill.
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