Review on gaseous chlorinated organic pollutants electron beam treatment

Literature on chlorinated organic compounds (Cl–HC) treatment in different conditions using EB-irradiation was reviewed and results of the studies are reported, and compared with own results. The differences in degradation efficiency of aliphatic and aromatic Cl–HC compounds were compared. The experiments and the calculations were performed for air, N₂, He and H₂ gas matrices and influence of different additives such as water vapour and NH₃ on the process were studied. The general chemical mechanism of Cl–HC degradation in gas phase under EB-irradiation has been proposed.     

State-of-the-art of gas chromatography-based methods for analysis of anthropogenic volatile organic compounds in estuarine waters,illustrated with the river Scheldt as an example

This review focuses on a number of key procedural steps in the analysis of volatile organic compounds (VOCs) in estuarine waters. The most critical step, from an analytical point of view, is sample preparation. So far, only purge-and-trap and, to some extent, membrane inlet mass spectrometry have successfully been applied in estuarine monitoring of VOCs. The advantages and disadvantages of both techniques are discussed and novel developments are reviewed. Other key elements in VOC analysis and assessment include quality assurance (QA), quality control (QC) and statistical data analysis. This paper gives a brief overview of QA/QC measures of interest in the estuarine monitoring exercise, and provides guidelines for adequate statistical treatment of environmental data. Finally, field measurements of VOCs in estuarine waters are reviewed. Concentrations are reported, and distribution patterns, sources and time-trends are discussed. In addition to literature data, results of a 3-year monitoring survey (May 1998–November 2000) in the Scheldt estuary are presented.     

Rapid analysis of environmental samples using solid-phase microextraction (SPME) and narrow bore capillary columns

The application of SPME, a solventless extraction procedure, is demonstrated for two environmental applications. Extraction of VOCs by SPME is coupled with analysis on short narrow bore capillary gas chromatography columns. The technique is shown both as a fast screening tool and as part of an analytical procedure when combined with a mass spectrometer. Data show the linear range of the procedure. The extraction of chlorinated pesticides from hazardous wastewater and drinking water by SPME is also described in this paper. SPME is compared to traditional extraction procedures with respect to cost, time, ease of use, solvent usage, and sample usage.     

Chlorinated Organic Compounds Decomposition in a Dielectric Barrier Discharge

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%.     

Vergleichbare Kraftfelder vieratomiger Formylverbindungen

Comparable force fields for HCOO^–, HFCO, HClCO and HDCO have been calculated on the basis of internal coordinates. Linear relations between (i) the carbonyl bond order and the carbonyl stretching force constant, (ii) the sum of the three in-plane bending force constants and the hydrogen out-of-plane force constantf , (iii) a combination of orbital electronegativities andf , have been obtained. The observed in-plane vibrational frequencies have been calculated with an average error of 6.3 cm^–1 or 0.4%.

     

RPS／CPE的反应性共混及其对PS／PE的增容作用

用ＦＴＩＲ、ＤＳＣ等方法研究了含恶唑啉官能力的聚苯乙烯（ＲＰＳ）与氯化聚乙烯（ＣＰＥ）之间的反应。ＲＰＳ、ＣＰＥ、ＰＳ、ＰＥ在不同温度下用反应式挤出要熔融共辊，结果表明，ＲＰＳ／ＣＰＥ对ＰＳ／ＰＥ共混物具有增容作用，提高了共混物的力学性能。此反应性共混适宜在较低温度下进行，对ＲＰＳＣＰＥ共混物还进行了动态力学表征，并与ＲＰＳ进行比较以进一步了解共混物的特征。     

Response of halogenated compounds in ion mobility spectrometry depending on their structural features

Ion mobility spectrometry (IMS) with handheld and transportable devices permits the sensitive detection of chlorinated compounds which are important in environmental monitoring. The ion mobility spectra in negative measuring modus mostly show one product ion peak [(H₂O)_nCl⁻] due to dissociative electron attachments. In this paper, we investigated relevant chlorinated compounds (R-Cl) where R represents allyl-, benzyl-, phenyl-, alkyl- and vinyl-groups. These groups cause differences in the R-Cl bond strength and differences in the cleavage of chlorine can therefore be expected. All chlorinated substances investigated provide the same product ion peak at 2.75 cm² Vs⁻¹ independent on the different C-Cl bond strength. However, distinct influences of structural features on the peak intensities of the (H₂O)_nCl⁻ product ion peak were established. Generally, increasing sensitivities were obtained in the order chlorobenzenes < vinyl- < allyl- < alkyl compounds < benzylchlorides. Sensitivities and limits of detection (LODs) of aromatic compounds depend on the nature and position of second substituent. Electron-withdrawing substituents (chlorine, fluorine, nitrile) enhance sensitivity while electron-repelling substituents decrease it. A dependence of sensitivity on the chain length or ring size can be observed for alkyl compounds. Additional influences of intramolecular interactions on the sensitivity were found for di-halogenated compounds. Therefore, the quantification of negative product ion peaks of chlorinated compounds requires a consideration of structural features of analytes.     

Programmed-Temperature Vaporizing (PTV) Liners to Introduce Chlorinated and Sulfur Compounds into a Capillary Gas Chromatograph

Introduction of a sample at a programmed temperature is an attractive approach both for dilute samples in large volumes and to prevent discrimination inside the syringe needle with this injection into a capillary gas Chromatograph. Quantitative data obtained with glass liners packed with trapping materials including glass wool, Tenax TA, Chromosorb 101 and Thermotrap-TA to analyze chlorinated and sulfur compounds are compared. To eliminate the solvent, these vapors were vented through the injection port cap, which provided greater efficiency than through the split line.     

Quantitative Analysis of Persistent Organochlorines in Samples From Polar Regions a Challenge For The Analytical Chemist

Abstract

The study of the transport and fate of persistent polychlorinated compounds to remote areas such as polar regions requires analytical methods which are capable to detect fg to pg amounts in the main transport medium, the atmosphere, as well as their accumulation in the very short food chain. A list of requirements are given which have to be fulfilled for the detection of such compounds with sufficient reliability. Furthermore, problems observed during sample clean-up, separation and quantification of such low levels are discussed using practical examples, and proposals are made how to avoid them.     

Calculation of optimum geometries and force fields by the CNDO/force method

CNDO/Force calculations have been performed on a series of molecules, H₂CO, F₂CO, CF₄, CHF₃, CH₂F₂ and CH₃F. The optimum geometries and force fields are reported. It is found that the method can successfully predict the geometries of polyatomic molecules. The bending force constants and interaction force constants are, in general, comparable with experimental values both with respect to sign and magnitude. The stretching force constants have higher values than the experimental force constants. However, the trend in stretching force constants of a series of molecules is comparable with that of the corresponding experimental values.     

Comparison of simultaneous distillation extraction and solid-phase microextraction for the determination of volatile flavor components

Traditional simultaneous distillation extraction (SDE) and solid-phase microextraction (SPME) techniques were compared for their effectiveness in the extraction of volatile flavor compounds from various mustard paste samples. Each method was used to evaluate the responses of some analytes from real samples and calibration standards in order to provide sensitivity comparisons between the two techniques. Experimental results showed traditional SDE lacked the sensitivity needed to evaluate certain flavor volatiles, such as 1,2-propanediol. Dramatic improvements in the extraction ability of the SPME fibers over the traditional SDE method were noted. Different SPME fibers were investigated to determine the selectivity of the various fibers to the different flavor compounds present in the mustard paste samples. Parameters that might affect the SPME, such as the duration of absorption and desorption, temperature of extraction, and the polarity and structure of the fiber were investigated. Of the various fibers investigated, the PDMS–DVB fiber proved to be the most desirable for these analytes.     

Improving the accuracy of carbon-to-hydrogen ratio determination for P,N, S,O, Cl,and Br-containing organic compounds using atomic emission detection

The objective of this work was to investigate the dependence of atomic emission detector C and H response on microwave-induced plasma conditions and to improve the accuracy of carbon-to-hydrogen ratio determination for trialkylphosphates, herbicides, chlorophenols, and sulfur-containing organic compounds. Compounds which differed structurally from the analytes were used as reference compounds. It was found that when the oxygen concentration in the helium was the maximum for the instrument (9%) relative errors in carbon-to-hydrogen ratio determination were 3–8%, irrespective of analyte and reference compound structure, whereas when working in the mode of operation recommended by the manufacturer of the instrument (1.5% oxygen in helium) the respective errors were 10–20% or higher. This improvement in the accuracy of carbon-to-hydrogen ratio determination was accompanied by a factor of ten decrease in sensitivity.     

元素有机化合物在有机合成中的应用

本文简要介绍磷、硫、砷、硅、硼和锡有机化合物在有机合成应用中研究得较活跃的一些例子,并着重讨论应用元素有机化合物合成立体专一性、光学活性和生理活性的化合物。