排序方式: 共有36条查询结果,搜索用时 15 毫秒
31.
Matt V. Alexander 《Microchemical Journal》2008,88(1):38-44
Trichloroethylene (TCE), a useful industrial agent which unfortunately exhibits carcinogenic properties, has become an extremely prevalent environmental contaminant. As such, new rapid, sensitive, and cost effective detection methods are needed for the identification of potential point sources of contamination. A new analytic micro-headspace method is described, utilizing solid phase micro-extraction (SPME) fibers and routine gas chromatography/electron capture detection (GC/ECD) for the detection of TCE to the 3.89 ppb level in aqueous samples. The polydimethylsiloxane (PDMS) fiber was shown to have the greatest analytical promise, with excellent sensitivity and minimal carry over. This method was employed in the monitoring of the photo-oxidation of TCE using buoyant TiO2 coated microspheres, which were sensitized using natural anthocyanin dyes obtained from fruits. Solar mediated photo-oxidation was shown to be a successful method for the removal of aqueous organic contaminants. The dye sensitized system yielded excellent remediation with 93% of the TCE removed from the system within 12 h. As irradiation was executed, overall TCE concentrations were reduced, while the expected mineralization product of hydrochloric acid was produced. The micro-headspace SPME procedure described here, offers considerably improved sensitivity, with orders of magnitude improvement in method detection limits, over previously published micro-headspace methods. 相似文献
32.
M. Magureanu N. B. Mandache V. I. Parvulescu 《Plasma Chemistry and Plasma Processing》2007,27(6):679-690
The decomposition of chlorinated volatile organic compounds by non-thermal plasma generated in a dielectric barrier discharge
was investigated. As model compounds trichloroethylene (TCE) and 1,2-dichloroethane (DCE) were chosen. It was found that TCE
removal exceeds 95% for input energy densities above 0.2 eV/molecule, regardless of the initial concentration of TCE, in the
range 100–750 ppm. On the other hand, DCE was more difficult to decompose, the removal rate reached a maximum of 60% at the
highest input energy used. For both investigated compounds the selectivity towards carbon dioxide was significantly influenced
by their initial concentration, increasing when low concentrations were used. The gas flow rate had also an effect on CO2 selectivity, which is higher at low flow rate, due to the higher residence time of the gas in the plasma. The best values
obtained in these experiments were around 80%. 相似文献
33.
34.
V.M. Bermudez 《Surface Science Reports》2017,72(4):147-315
A review is presented that covers the experimental and theoretical literature relating to the preparation, electronic structure and chemical and physical properties of the surfaces of the wurtzite form of GaN. The discussion includes the adsorption of various chemical elements and of inorganic, organometallic and organic species. The focus is on work that contributes to a microscopic, atomistic understanding of GaN surfaces and interfaces, and the review concludes with an assessment of possible future directions. 相似文献
35.
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
36.
Low energy electron beam treatment of VOCs 总被引:1,自引:0,他引:1
Shoji Hashimoto Teruyuki Hakoda Koichi Hirata Hidehiko Arai 《Radiation Physics and Chemistry》2000,57(3-6):485-488
Research on electron beam decomposition of volatile organic compounds (VOCs) in air was carried out to establish an advanced treatment technology for industrial off-gases. Benzene, toluene and o-xylene were selected as aromatic VOCs and dichloro-, trichloro- and tetrachloro-ethylene as chloroethenes. The experimental results showed that G-values of decomposition ranged from 1.0–2.2 in aromatic compounds and 30–60% of decomposed compounds were converted into aerosols. On the other hand, G-values of decomposition of chloroethenes increased with the initial concentration and number of chlorine atoms in a molecule, for example, the G-value at 180 and 1580 ppm of tetrachloroethylene were 22 and 172, respectively. The formation of aerosol was not observed in the decomposition of chloroethenes. An application of low energy electron accelerator for treatment of exhaust gases containing VOCs was also discussed. 相似文献