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  • Organochlorine and organophosphorus pesticides  (2)
  • 61.70.At  (1)
  • 1
    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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  • 2
    Electronic Resource
    Electronic Resource
    Optical properties of laser-processed In x Ga1−x As (1994)
    Springer
    Applied physics 59 (1994), S. 617-621 
    Details
    ISSN: 1432-0630
    Keywords: 78.30.Fs ; 68.55.Nq ; 61.70.At
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Various spots in GaAs, In-diffused with the 1.064 μm line of pulsed Nd:YAG laser with several energy densities, have been characterized and compared with samples prepared by the conventional rapid thermal annealing method. Of the energy densities used, the spot processed with an energy density of 7 J/cm2 shows In x Ga1−x As phases with an indium concentration of 60% and below. An abrupt boundary in the indium concentration is observed at the edge of the laser-annealed spot. The diffusion depth is found to be less than 1000 Å. The spot processed with an energy density of 14 J/cm2 shows considerable damage from the irradiation resulting in strain in the lattice. The samples prepared by the thermal annealing method show similar results to the laser-diffused samples. However, these thermally annealed samples suffer from arsenic loss unlike the laser-processed samples. It can be concluded that laser-induced alloying of indium into GaAs can be achieved with less arsenic loss than the thermal annealing method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00331922
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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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