Zinc-catalyzed Williamson ether synthesis in the absence of base

Zinc powder was found to be a highly efficient catalyst for the synthesis of aromatic ethers using microwave heating in the presence of N,N-dimethylformamide as well as under stirring in an oil-bath using tetrahydrofuran as solvent without any inorganic base. This method can be used for selective mono-, di- or tri-O-alkylations.     

呋喃西林水溶液在光和热作用下的稳定性

The influence of both light and heat on the stability of nitrofurazone aqueous solution was studied. Results show that in either heating experiments or the exposure to light at high temperatures, the degradation rate obeyed zero-order kinetics. The total rate constant ktotal caused by both light and heat can be divided into two parts: ktotal =kdark klight, where kdark and klight are the degradation rate constants caused by heat and light, respectively. The klight can be expressed as klight=Alight*exp(-Ea,light/RT)*E, where E is the illuminance of light, and Alight and Ea,light both are experimental constants. The values of these kinetic parameters were determined based on the experiments in the dark and upon exposure to three different light sources. Results show that the values of Alight and Ea, light varied with the light source. To save time, labor, and drugs, exponential heating experiments were employed and compared with the isothermal experiments. Results indicated that kinetic parameters obtained by exponential heating experiments are comparable to those obtained by isothermal experiments either in the dark or upon exposure to light.     

Temperature programmed desorption analysis of sol-gel-derived titania films

Sol-gel-derived titania films were analyzed by temperature programmed desorption (TPD) and X-ray diffraction (XRD) techniques. The relationship between the TPD curves measured for two types of titania gel films and their crystal structures was investigated. On the basis of the analyses, a preparation process for a titania sol solution containing anatase nanocrystals was designed and developed. Using this process, a colloidal anatase titania sol solution was prepared by heating aqueous titanium hydroxide containing HCl at 60°C for 2 h. The nanocrystal structure of the titania films obtained by coating the sol on glass substrates was confirmed by TPD and XRD measurements.     

液相微波介电加热法制备纳米粒子的研究进展

随着纳米科技的飞速发展,合成纳米材料的新方法层出不穷。在这些新方法当中,液相微波介电加热法近年来得到了飞速的发展,引起了科学界越来越多的关注。本文介绍了近年来液相微波介电加热法制备纳米粒子的一些研究进展,主要是该方法在制备金属、过渡金属氧化物和金属硫族化合物纳米粒子中的应用,并且对该领域未来的发展作了一些展望。     

Faster GC analyses performed by flow programming in short capillary columns

The technique of programming the carrier gas flow rate in gas chromatography, especially in connection with the use of capillary columns shorter than 10 m can significantly accelerate GC analyses. Equations for calculation of the parameters of the exponential flow function and retention data are described. The effects of flow programming in a short capillary column are shown in a few chromatograms. Different programming rates are tested and compared with temperature programming.     

Highly efficient approach for characterizing nanometer-sized gold particles by capillary electrophoresis

This paper demonstrates that capillary electrophoresis (CE) can be employed for characterizing the sizes of nanometer-scale gold particles. We characterized the gold nanoparticles by effecting CE separation using a buffer of SDS (70 mM) and 3-cyclohexylamino-1-propanesulfonic acid (CAPS; 10 mM) at pH 11.0 and an applied voltage of 18 kV and obtained a linear relationship (R² > 0.99) between electrophoretic mobilities and size for nanoparticles whose diameters fall in the regime from 5.0 ± 0.5 to 41.2 ± 3.3 nm; the relative standard deviations of these electrophoretic mobilities are <0.8%. We evaluated the feasibility of employing these separation conditions for the size characterization by of gold nanoparticle samples that were synthesized by a rapid microwave heating method. We confirmed that this CE method is a valid one for size characterization by comparing the results obtained by CE with those provided by scanning electron microscopy (SEM); a good correlation exists between these two techniques. Our results demonstrate that CE can be employed to accelerate the analysis of the sizes of nanomaterials.     

Closed tube sample introduction for gas chromatography-ion mobility spectrometry analysis of water contaminated with a chemical warfare agent surrogate compound

Ion mobility spectrometry (IMS) is a proven technology for detection of vapor phase chemical warfare agents. The technology is suitable for field portable instrumentation due to its small size, high sensitivity, speed of analysis, and low power consumption. However, it suffers from a limited dynamic range and potential difficulties in identifying compounds in complex matrices. The use of gas chromatography (GC) coupled to IMS can overcome the difficulty of chemical identification in mixtures by separating the sample into individual components before detection. Using this approach, IMS technology has previously been adapted to detect biological aerosols using an open tube pyrolyzer and a short GC column (Py-GC-IMS). The open sample introduction tube of a Py-GC-IMS instrument would be a convenient configuration to accept aerosol particulates, and while viewed as needed for aerosol trapping, is not optimal for liquid chemical analyses. To examine the usefulness of an existing Py-GC-IMS system for analysis of chemicals in water, an existing open-port sample interface was replaced with a septum-equipped closed tube injector to contain analyte vapors resulting from liquid injection. Tributylphosphate (TBP) was used as a surrogate chemical warfare agent, and aqueous injections into both closed and open tube assemblies were performed. Sample introduction into the closed tube inlet was also accomplished using solid phase microextraction (SPME) preconcentration. The limit of detection for TBP using an open tube, closed tube, and closed tube configuration with SPME sample introduction was 0.980, 0.196, and 0.0098 mg/L, respectively.     

担体对Fe-MnO催化剂CO加氢合成烯烃性能影响的TPSR表征

考察了不同担体担载的Ｆｅ－ＭｎＯ催化剂上ＣＯ加氢合成烯烃的反应。结果表明担体直接影响低碳烯烃选择性。通过对催化剂的ＣＯ，ＣＯ／Ｈ２，Ｃ２Ｈ４等吸附的ＴＰＳＲ表征及催化剂表面ＣＯ加氢微观反应的研究，证明以碱性担体为基质的ＰＢＣ催化剂具有强吸附ＣＯ能力，且生成的烯烃不易发生二次反应，因而ＰＢＣ催化剂具有较高的烯烃选择性；以酸性担体为基质的ＰＡＣ催化剂对ＣＯ为弱吸附，对Ｈ２为较强吸附，且烯烃会发生强烈的     

微波增压溶样-石墨炉原子吸收光谱法同时测定植物性样品中微量铅镉

使用微波增压溶样法，将样品用HNO3—HClO4溶解后，用石墨炉原子吸收光谱法同时测定植物性样品中铅和镉。以磷酸二氢铵—硝酸镁作为基体改进剂，可使灰化温度大大提高，克服了基体的干扰。铅和镉的回收率分别为95．3％—104．8％和96．2％—105．5％，RSD分别为4．8％-7．2％和4．3％-7．6％。