Experimental study of the gas-phase hydrofluorination of perchloroethylene over a chromium-based catalyst

Summary Gas-phase hydrofluorination of perchloroethylene to pentafluoroethane in the presence of a chromium-magnesium catalyst at 0.4 MPa and 330-390°C has been studied. А reaction scheme taking into account the formation of by-products is suggested. An erratum to this article is available at .     

Application of solid phase microextraction and needle trap device with silica composite of carbon nanotubes for determination of perchloroethylene in laboratory and field

In this paper solid phase microextraction (SPME) and needle trap device (NTD) as two in-progress air monitoring techniques was applied with silylated composite of carbon nanotubes for sampling and analysis of perchloroethylene in air. Application of SPME and NTD with proposed nano-structured sorbent was investigated under different laboratory and experimental parameters and compared to the SPME and NTD with CAR/PDMS. Finally the two samplers contained nano-sorbent used as a field sampler for sampling and analysis of perchloroethylene in dry cleaning. Results revealed that silica composite form of CNTs showed better performance for adsorbent of perchloroethylene. SPME and NTD with proposed sorbent was demonstrated better responses in lower levels of temperature and relative humidity. For 5 days from sampling the relative responses were more than 97% and 94% for NTD and SPME, respectively. LOD were 0.023 and 0.014 ng mL⁻¹ for SPME coated CNTs/SC and CAR/PDMS, and 0.014 and 0.011 ng mL⁻¹ for NTD packed with CNTs/SC and CAR/PDMS, respectively. And for consecutive analysis RSD were 3.9–6.7% in laboratory and 4.43–6.4% in the field. In the field study, NTD was successfully applied for determining of the PCE in dry cleaning. The results show that the NTD packed with nanomaterial is a reliable and effective approach for the sampling and analysis of volatile compounds in air.     

OH与TCE和PCE加成中间体消除反应的机理

用从头计算法在UHF/6-31G水平研究了羟基自由基与三氯乙烯和四氯乙烯形成的加成中间体的消除反应,通过振动分析确认了过渡态,计算了内禀反应坐标(IRC).研究表明,该反应消除一个氯化氢分子,形成具有平面构型的另一个中间体,反应活化势垒较低,分别为79.84kJ mol-1和62.68kJ mol-1,且二者反应在常温常压下是熵增、放热、吉布斯自由能ΔGΘ<Ο,具有较大自发趋势的过程。     

Multiple headspace extraction—A procedure for eliminating the influence of the sample matrix in quantitative headspace,gas chromatography

Summary A stepwise gas extraction procedure is described for the quantitative gas chromatographic analysis of volatile compounds in solid and liquid samples. This procedure is a modification of the usual headspace analysis and can be carried out with the same equipment, provided a pressure and time controlled sampling system is used. This procedure is called Multiple Headspace Extraction (MHE) therefore. This method has first been developed for the analysis of monomers in polymers and residual solvents in printed films, but it is shown that can be applied to various other sample types also including even liquid samples.Dedicated to L. S. Ettre on the occasion of his 60th birthday.