ZnO-coated glass fibers for the analysis of trihalomethanes by headspace-solid phase microextraction-gas chromatography

Li₂O-ZrO₂-BaO-SiO₂ glass fibers were produced and their surfaces were coated with zinc oxide. The fibers’ surface morphology was examined by scanning electron microscopy and the zinc oxide layer was characterized by mapping the K_α and L_α lines of zinc by energy dispersive X-ray spectroscopy. The results indicated that a homogeneous and porous layer of ZnO was formed on the fibers’ surface. This layer was subjected to a simultaneous determination of trihalomethanes using headspace-solid phase microextraction-gas chromatography. The study was conducted after evaluating the ideal time of incubation (15 min), extraction (15 min) and desorption (10 min), as well as the effect of the addition of salt (15%, m/v) on the analytical response. A good linear dynamic range was observed individually for trihalomethanes aqueous solutions containing 20 μg L⁻¹ and 500 μg L⁻¹ of trichloromethane, 15 μg L⁻¹ and 250 μg L⁻¹ of dichlorobromomethane and dibromochloromethane and 10 μg L⁻¹ and 100 μg L⁻¹ of tribromomethane, with all the compounds showing correlation coefficients higher than 0.9900.     

Brom und Jod

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Induction period of the conversion of methanol to hydrocarbons on a nickel loaded faujasite: Evidence for a suppression of the autocatalytic step

The conversion of methanol to hydrocarbons on nickel loaded faujasites can be retarded for many hours time-on-stream. The induction period is interpreted to be due to a suppression of the autocatalytic step of the reaction. An autocatalytic mechanism is proposed based on the -scission of branched carbenium ion intermediates.

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有机硅活性中间体的研究 II. 一些含环丙基的有机硅化合物的合成及其结构

用锂有机物的方法合成了四种含有环丙基有机硅化合物,对上述每种化合物中可能存在着的立体异构进行了分离和和构型测定。     

Integral Representations for the Deflection and the Slope of a Plate on an Elastic Foundation

With the help of two fundamental solutions, integral representations for the deflection and the slope of polygonal shaped plates on an elastic foundation are derived. The kernel functions are evaluated in terms of zero-order Kelvin- or Thomson-functions and their derivatives, respectively. This revised version was published online in August 2006 with corrections to the Cover Date.     

Gasofen

Ohne Zusammenfassung