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  • Organochlorine and organophosphorus pesticides  (2)
  • Cu oxidation  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Oxidation of copper and electronic transport in copper oxides (1993)
    Springer
    Oxidation of metals 39 (1993), S. 411-435 
    Details
    ISSN: 1573-4889
    Keywords: Cu oxidation ; electrical conductivity ; defect mechanism ; defect mobility ; nonstoichiometry ; copper oxides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Oxidation of copper and electronic transport in thermally-grown large-grain polycrystals of nonstoichiometric copper oxides were studied at elevated temperatures. Thermogravimetric copper oxidation was studied in air and oxygen at temperatures between 350 and 1000°C. From the temperature dependence of the oxidation rates, three different processes can be identified for the oxidation of copper: bulk diffusion, grain-boundary diffusion, and surface control with whisker growth; these occur at high, intermediate, and low temperatures, respectively. Electrical-conductivity measurements as a function of temperature (350–1134°C) and oxygen partial pressure (10−8–1.0 atm) indicate intrinsic electronic conduction in CuO over the entire range of conditions. Electronic behavior of nonstoichiometric Cu2O indicates that the charge defects are doubly-ionized oxygen interstitials and holes. The calculated enthalpy of formation of oxygen ( $$\Delta H_{{\text{O}}_{\text{2}} }$$ ) and hole-conduction energy (EH) at constant composition for nonstoichiometric Cu2O are 2.0±0.2 eV and 0.82±0.02 eV, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00664664
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  • 2
    Electronic Resource
    Electronic Resource
    Sulfuric acid pretreatment for the simultaneous GC screening of organochlorine and organophosphorus pesticides in herbal essential oils (1998)
    Springer
    Chromatographia 47 (1998), S. 587-592 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Organochlorine and organophosphorus pesticides ; Herbal medicine ; Essential oils ; Sulfuric acid treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A rapid and new clean-up method utilizing sulfuric acid treatment is demonstrated to identify and quantify the level of organochlorine (OC) and organophosphorus (OP) pesticide residue concentrations in herbal essential oils by gas chromatography (GC). Essential oils fortified with pesticides, that are extracted from herbs by steam distillation are partitioned with 65% acetonitrile/water(v/v) and treated with sulfuric acid at different reaction times and sulfuric acid concentrations. Optimal conditions, to avoid interference from essential oils in gas chromatographic analysis, is 17% (v/v) of a mixed phase ratio of sulfuric acid to organic solvent (hexane/ethyl ether=9∶1, v/v) and a reaction time of 30s. The response of the flame ionization detector (FID) is linear for all pesticides determined. Recovery of pesticides from fortified herbs studied are in the range of 75% to 111% (RSD, 4% to 11%) for OC, and 72% to 116% (RSD, 2% to 11%) for OP. Although sulfuric acid treatment destroys carbamate and some organophosphorus pesticides, this method has efficiently reduced matrix interference and provides a rapid, economical clean-up method with excellent linear data having low coefficients of variation for the GC analyses of BHC isomers, DDD, DDE, DDT, chlorothalonil, chloropyrifos, tetradifon, fenitrothion, malathion, and parathion in matrices of herbal essential oils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467500
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  • 3
    Electronic Resource
    Electronic Resource
    Analysis of multi-component pesticide residues in herbal medicines by GC-MS with electron impact ionization and with positive- and negative-ion chemical ionization (1999)
    Springer
    Chromatographia 49 (1999), S. 525-534 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography-mass spectrometry ; Organochlorine and organophosphorus pesticides ; Herbal medicines ; Selective-ion monitoring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Multicomponent pesticide residues in herbal medicines have been analyzed by gas chromatography-mass spectrometry (GC-MS) with electron impact (EI) ionization and positive- and negative-ion chemical ionization (PCI and NCI). Herbal medicines (5 g) were extracted with 65∶35 (%,v/v) acetonitrile-water, and partitioned with hexane-diethyl ether (1∶1) and hexane-dichloromethane (1∶1). The organic phase of the extracted fraction was cleaned on a Florisil column and analyzed by GC-MS with selected-ion monitoring (SIM). Method detection limits for 27 pesticides were tens of picograms for ECD, NPD and EI-SIM MS, and a few picograms for NCI-SIM MS. The calibration curve for the pesticide standard solution was linear within the range 0.003–30 pg for EI-SIM MS, PCI-SIM MS, and NCI-SIM MS. Mean recoveries of pesticides from spiked herbal medicines (0.75, 1.5, 3 pg) were 61–125% (RSD1–32%) for NCI-SIM MS and 74–121% (RSD 4–12%) for EI-SIM MS. Detection sensitivity and specificity of NCI-SIM MS were better than for ECD and NPD. Parallel use of EI-SIM MS, PCI-SIM MS and NCI-SIM MS was an excellent complementary method for identification and confirmation of multi-component pesticide residues in variety of herbal medicines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467753
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