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The adsorption isotherms at 25, 45, and 65 degrees C of molybdenum solutions of concentration ranges between 10(-3) and 3x10(-2) M(Mo) (pH 4-5) on different alumina samples are investigated. The analysis is conducted using a modified Frumkin isotherm which takes a more realistic account of the lateral interaction between adsorbed species and considers that the adsorption takes place on the most basic OH groups on the surface of alumina. The results are discussed in view of the difference in solutions speciation, and the changes in the pH of the remaining supernatant solutions. The solution temperature, PZC of the used aluminas, the configuration of the basic OH groups on their surface, and the pore structure have been shown to intervene effectively. Copyright 2000 Academic Press. 相似文献
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Acosta-Tejada GM Medina-Peralta S Moguel-Ordóñez YB Muñoz-Rodríguez D 《Analytical and bioanalytical chemistry》2011,400(3):885-891
Five organophosphorus pesticides (dichlorvos, diazinon, malathion, methyl parathion and coumaphos) were extracted from propolis
by matrix solid-phase dispersion (MSPD) extraction using octadecylsilica (C18, 1.0 g) as dispersant material. The kind of
solvent elution (acetonitrile or ethyl acetate), volume (8 mL and 15 mL), and adsorbent used to clean-up the extracts (graphitized
carbon, florisil™ and silica) were optimized using fortified propolis samples (5.0 μg g−1). Recovery was determined by gas chromatography with mass spectrometric detection in selected ion monitoring mode (GC/MS-SIM)
and statistical analysis was done to determine better extraction conditions. Relatively high recovery and lower relative standard
deviation values (3.1–14.6%) were obtained when analytes were eluted with ethyl acetate from the MSPD column. Diazinon, malathion,
methyl parathion, and coumaphos show recoveries of 72.7%, 84.6%, 62.6%, and 78.3%, respectively. In contrast, the recovery
for dichlorvos was 53.8%. Additional adsorbents tested for clean-up and increase in solvent elution did not affect recoveries
positively and caused a high background in chromatograms. Thus, final conditions were 1 mL of sample, 1 g C18 and 8 mL of
ethyl acetate. 相似文献
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