排序方式: 共有66条查询结果,搜索用时 15 毫秒
61.
Weradeach Sangkhun Laksana Laokiat Visanu Tanboonchuy Pummarin Khamdahsag Nurak Grisdanurak 《Superlattices and Microstructures》2012
W-doped TiO2 were immobilized on fiberglass cloth (FGC). The catalyst possessed small crystallite sizes with a red-shift on an absorption edge. Good dispersion was observed over the immobilized catalyst. The photocatalytic degradation of gaseous BTEX was conducted in a flow reactor under day-light fluorescent. Parameters including gas flowrate, catalyst loading, initial concentration and relative humidity (%RH) were investigated. The prepared catalysts showed higher efficiency than that of TiO2 approximately 18, 3, 3 and 2.5× for benzene, toluene, ethylbenzene and o-xylene, respectively. The condition to achieve 100% BTEX removal was found at 20 min/ml, catalyst loading 0.1 mg/cm2 and 30% RH. 相似文献
62.
Solid phase microextraction (SPME) was used as the sample introduction technique for high-speed isothermal GC. An injector dedicated for SPME fiber injection was designed and built. The injector was operated in two modes, continuously heated and flash heated. The latter mode proved to be better for high-speed separations. The injector was then used for sample introduction in separation of BTEX. When sampling directly from water with a fiber having a 56 μm thick poly(dimethylsiloxane) coating, the BTEX components were separated under isothermal conditions in ca. 18 s. A fiber with a thinner coating (15 μm) enabled the separation to be completed in ca. 12 s when sampling from headspace. In both cases the results were highly reproducible, as measured by the estimated values of the relative standard deviation. 相似文献
63.
On-column injection system for use of large diameter inside needle capillary adsorption trap devices
Direct coupling of the needle trap to the capillary column in the split/splitless gas chromatographic (GC) inlet with simple modification facilitates full exploitation of the column efficiency, even when using the large volume trap filled with 35 mg of Tenax TA. A schematic diagram of the inlet and of the new modification of the INCAT device and an example of BTEX (benzene, toluene, ethylbenzene and xylenes) analysis is presented. Determination of the repeatability of BTEX analyses resulted in relative standard deviations of 2.4–3.6%. 相似文献
64.
Mariusz Marć Jacek Namieśnik 《International journal of environmental analytical chemistry》2013,93(2):151-167
This paper presents the results of atmospheric air quality research in Tczew (adjacent to the Vistula River) on the content of BTEX compounds. procedure applied during the sampling of the analytes from the air used the passive sampling technique (diffusive passive sampler, Radiello®). For determination of BTEX compounds in atmospheric air, two-stage thermal desorption technique combined with gas chromatography (TD-GC-FID) was applied.Research was conducted from March to December 2011. The annual average concentration of benzene, toluene, ethylbenzene and total xylenes determined in atmospheric air for the monitoring period were: 0.87 μg m–3, 2.9 μg m–3, 1.3 μg m–3 and 5.9 μg m–3, respectively. In order to pre-identify potential sources of emissions of BTEX compounds, statistical analysis was carried out. This determined interactions between specified concentration levels of BTEX compounds in atmospheric air for the monitored area. 相似文献
65.
A novel design of solid phase microextraction fiber containing carbon nanotube reinforced sol-gel which was protected by polypropylene hollow fiber (HF-SPME) was developed for pre-concentration and determination of BTEX in environmental waste water and human hair samples. The method validation was included and satisfying results with high pre-concentration factors were obtained. In the present study orthogonal array experimental design (OAD) procedure with OA(16) (4(4)) matrix was applied to study the effect of four factors influencing the HF-SPME method efficiency: stirring speed, volume of adsorption organic solvent, extraction and desorption time of the sample solution, by which the effect of each factor was estimated using individual contributions as response functions in the screening process. Analysis of variance (ANOVA) was employed for estimating the main significant factors and their percentage contributions in extraction. Calibration curves were plotted using ten spiking levels of BTEX in the concentration ranges of 0.02-30,000ng/mL with correlation coefficients (r) 0.989-0.9991 for analytes. Under the optimized extraction conditions, the method showed good linearity (0.3-20,000ng/L), repeatability, low limits of detections (0.49-0.7ng/L) and excellent pre-concentration factors (185-1872). The best conditions which were estimated then applied for the analysis of BTEX compounds in the real samples. 相似文献
66.
Schmidt TC Zwank L Elsner M Berg M Meckenstock RU Haderlein SB 《Analytical and bioanalytical chemistry》2004,378(2):283-300
Compound-specific stable isotope analysis (CSIA) using gas chromatography-isotope ratio mass spectrometry (GC/IRMS) has developed into a mature analytical method in many application areas over the last decade. This is in particular true for carbon isotope analysis, whereas measurements of the other elements amenable to CSIA (hydrogen, nitrogen, oxygen) are much less routine. In environmental sciences, successful applications to date include (i) the allocation of contaminant sources on a local, regional, and global scale, (ii) the identification and quantification of (bio)transformation reactions on scales ranging from batch experiments to contaminated field sites, and (iii) the characterization of elementary reaction mechanisms that govern product formation. These three application areas are discussed in detail. The investigated spectrum of compounds comprises mainly n-alkanes, monoaromatics such as benzene and toluene, methyl tert-butyl ether (MTBE), polycyclic aromatic hydrocarbons (PAHs), and chlorinated hydrocarbons such as tetrachloromethane, trichloroethylene, and polychlorinated biphenyls (PCBs). Future research directions are primarily set by the state of the art in analytical instrumentation and method development. Approaches to utilize HPLC separation in CSIA, the enhancement of sensitivity of CSIA to allow field investigations in the µg L–1 range, and the development of methods for CSIA of other elements are reviewed. Furthermore, an alternative scheme to evaluate isotope data is outlined that would enable estimates of position-specific kinetic isotope effects and, thus, allow one to extract mechanistic chemical and biochemical information.Abbreviations BTEX
benzene, toluene, ethylbenzene, xylenes
- MTBE
methyl tert-butyl ether
- PAHs
polycyclic aromatic hydrocarbons
- VOCs
volatile compounds
- PCBs
polychlorinated biphenyls
- CSIA
compound-specific (stable) isotope (ratio) analysis
- GC-IRMS, GC/IRMS or GCIRMS
gas chromatography-isotope ratio mass spectrometry
- GC-C-IRMS, GC/C/IRMS or GCC-IRMS
gas chromatography-combustion-isotope ratio mass spectrometry
- irmGC/MS
isotope ratio monitoring gas chromatograph-mass spectrometry
- GC/P/IRMS
gas chromatography-pyrolysis-isotope ratio mass spectrometry (used for D/H)
- KIE
kinetic isotope effect
- PSIA
position-specific isotope analysis (for intramolecular isotope distribution)
- SNIF-NMR
site-specific natural isotopic fractionation by nuclear magnetic resonance spectroscopy 相似文献