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排序方式: 共有337条查询结果,搜索用时 125 毫秒
241.
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Quantification of bacterial lipopolysaccharides (endotoxin) by GC-MS determination of 3-hydroxy fatty acids 总被引:1,自引:0,他引:1
Binding N Jaschinski S Werlich S Bletz S Witting U 《Journal of environmental monitoring : JEM》2004,6(1):65-70
A GC-MS method for the quantification of bacterial lipopolysaccharides (LPS, endotoxin) is presented. After hydrolytic cleavage of 3-hydroxy fatty acids (3-OH FAs) from the lipid A region of LPS, derivatisation of both the hydroxyl and the carboxyl group was performed in one step with a mixture of methyl-bis(trifluoracetamide)(MBTFA) and N-methyl-N-(tert-butyldimethylsilyl)trifluoracetamide (MTBSTFA). Using GC-MS in the EI mode with selected ion monitoring (SIM) for analysis, baseline separation of 3-OH FAs (and of possibly interfering 2-OH FAs) was achieved. The sensitivity of the method (LOD 7-50 pg/injection for the different 3-OH FAs investigated) allows for the efficient quantification of LPS in occupational and environmental samples. Degradation of 3-OH FAs as well as of their derivatives during sample preparation and GC-MS separation as a possible source of errors in analytical methods based on 3-OH FA determination is reported for the first time. Thermal elimination of water from the underivatised 3-OH FAs and of trifluoroacetic acid from the derivatives was identified as the cause of degradation. The resulting alpha,beta-unsaturated compounds showing the same mass spectra as the 3-OH FA derivatives were detected as more or less prominent satellite peaks. By using alkaline instead of acidic hydrolysis and cool on-column instead of split/splitless injection, elimination was reduced to an acceptable level. 相似文献
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Treatment technologies for aqueous perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) 总被引:1,自引:0,他引:1
Chad D. Vecitis Hyunwoong Park Jie Cheng Brian T. Mader Michael R. Hoffmann 《Frontiers of Environmental Science & Engineering in China》2009,3(2):129-151
Fluorochemicals (FCs) are oxidatively recalcitrant, environmentally persistent, and resistant to most conventional treatment
technologies. FCs have unique physiochemical properties derived from fluorine which is the most electronegative element. Perfluorooctanesulfonate
(PFOS), and perfluorooctanoate (PFOA) have been detected globally in the hydrosphere, atmosphere and biosphere. Reducing treatment
technologies such as reverses osmosis, nano-filtration and activated carbon can remove FCs from water. However, incineration
of the concentrated waste is required for complete FC destruction. Recently, a number of alternative technologies for FC decomposition
have been reported. The FC degradation technologies span a wide range of chemical processes including direct photolysis, photocatalytic
oxidation, photochemical oxidation, photochemical reduction, thermally-induced reduction, and sonochemical pyrolysis. This
paper reviews these FC degradation technologies in terms of kinetics, mechanism, energetic cost, and applicability. The optimal
PFOS/PFOA treatment method is strongly dependent upon the FC concentration, background organic and metal concentration, and
available degradation time. 相似文献
248.
Angeborene Tagesperiodik bei Eidechsen 总被引:1,自引:0,他引:1
Klaus Hoffmann 《Die Naturwissenschaften》1957,44(12):359-360
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Chad D. VECITIS Hyunwoong PARK Jie CHENG Brian T. MADER Michael R. HOFFMANN 《Frontiers of Environmental Science & Engineering》2009,3(2):129-151
Fluorochemicals (FCs) are oxidatively recalcitrant, environmentally persistent, and resistant to most conventional treatment technologies. FCs have unique physiochemical properties derived from fluorine which is the most electronegative element. Perfluorooctanesulfonate (PFOS), and perfluorooctanoate (PFOA) have been detected globally in the hydrosphere, atmosphere and biosphere. Reducing treatment technologies such as reverses osmosis, nano-filtration and activated carbon can remove FCs from water. However, incineration of the concentrated waste is required for complete FC destruction. Recently, a number of alternative technologies for FC decomposition have been reported. The FC degradation technologies span a wide range of chemical processes including direct photolysis, photocatalytic oxidation, photochemical oxidation, photochemical reduction, thermally-induced reduction, and sonochemical pyrolysis. This paper reviews these FC degradation technologies in terms of kinetics, mechanism, energetic cost, and applicability. The optimal PFOS/PFOA treatment method is strongly dependent upon the FC concentration, background organic and metal concentration, and available degradation time. 相似文献