Infrared dichroism measurements on the alkyl chain packing of an ionic detergent intercalated between silicate layers

 Microcrystals of the metal silicate hydrate ilerite orient macroscopically on the surface of a ATR-crystals and thus, are accessible for infrared linear dichroism measurements. We present first results which indicate that the alkyl chain packing and the orientation of the polar group of dodecyltrimethylammoniumbromide (DTAB) intercalated between silicate layers can be determined in terms of infrared order parameters. The properties of DTAB can be modulated by the relative humidity of the surrounding atmosphere and by temperature. Upon heating DTAB undergoes a phase transition from a paraffin-like solid to a fluid phase. The former is characterized by the orthorhombic perpendicular packing of the frozen alkyl chains with tilted long axes. The interactions between the ionic groups of the surfactant and that of the host matrix stabilize the lamellar arrangement of DTAB in the crystalline and in the fluid phases. Received: 14 January 1998 Accepted: 27 July 1998     

分散固相萃取结合气相色谱-高分辨质谱快速筛查酱油中多种氯丙醇

建立了酱油中1，3-二氯-2-丙醇、2，3-二氯-1-丙醇、3-氯-1，2-丙二醇和2-氯-1，3-丙二醇的分散固相萃取-气相色谱-高分辨质谱快速筛查检测方法。样品采用乙酸乙酯提取，提取液浓缩后经N-丙基乙二胺净化，气相色谱-高分辨质谱测定，内标法定量。结果表明，该方法对于酱油中4种氯丙醇的定量限为0.5~10 μg/kg。在3个浓度水平下的加标回收率为78%~103%；相对标准偏差均不大于8.8%。该方法快速、简便、准确、灵敏，可作为酱油中4种氯丙醇的有效检测方法。     

Study of metal-loaded activated charcoals for the separation and determination of selenium species by energy dispersive X-ray fluorescence analysis

Conversion of adsorption properties of activated charcoal (C^∗) by metal modification towards selenite, selenate and seleno-dl-methionine (Se-Met) was studied. Several metals were included in modification studies and also a procedure was developed for the separation and independent determination of microgram quantities of these selenium species in aqueous solution. Selenium species were collected one by one from the same sample solution onto collector material by adsorbing them directly or after complex formation onto different metal-loaded activated charcoals (MgC^∗ and FeC^∗). The mass of selenium in these collectors was measured directly by energy dispersive X-ray fluorescence spectrometry (EDXRF). Detection limits for all three selenium species were better than 6 μg corresponding to concentration of 60 μg/l with 0.100 l of initial sample volume.     

离子液体的酸性测定及其催化的异丁烷／丁烯烷基化反应

 初次采用吡啶红外光谱探针法测定了离子液体的酸性．该方法能鉴别离子液体的Br¨onsted／Lewis酸类型，并可以粗略指示离子液体的Lewis酸强度．将［bmim］Cl／AlCl3类离子液体用于催化异丁烷与丁烯的烷基化反应，考察了酸强度、反应温度、压力和时间对产物分布的影响，并在最优操作条件下与传统的H2SO4催化剂进行了比较．结果表明，离子液体对烷基化反应的催化活性和选择性与H2SO4可比，而且它更容易与产物分离，不经任何处理可循环利用10次．     

Fourier transform infrared reflection-absorption spectroscopy of amino acids adsorbed on metal surfaces

Fourier transform infrared reflection-absorption spectroscopy (FT-IRAS) has been used to study the orientation and coordination of glycine, L-phenylalanine and L-histidine on gold and copper surfaces. It was found that glycine and L-histidine were weakly adsorbed (physisorbed) in the zwitterionic form on gold. The surface chemical bonding of L-histidine and L-phenylalanine to copper were chemical rather than physical by nature. Conclusive evidence was obtained for coordination to copper through both the amino-nitrogen and carboxylate-oxygen atoms.     

Chemical Liquid Phase Deposition of Thin Aluminum Oxide Films

Introduction Inorganic oxide films have attracted a lot of interest in the last several decades. Among them, silicon dioxide films are widely used in modern microelectronics, optics and mechanics. This material has been grown by various methods including thermal oxidation, chemical vapor phase deposition, plasma-enhanced chemical vapor phase deposition, and so on.1,2 Recently, Nagayama et al.3 have reported that SiO2 thin films could be produced by a new chemical method of liquid phase depos…     

Time‐resolved Fourier transform infrared/attenuated total reflection spectroscopy for the measurement of molecular diffusion in polymers

Over the past 2 decades, the use of time‐resolved Fourier transform infrared/attenuated total reflection (ATR) spectroscopy for the measurement of diffusion in polymers has grown. ATR is a powerful technique for the measurement of diffusion in polymers because it is an in situ technique that is relatively inexpensive, provides reliable short‐time data, and provides a wealth of information at the molecular level. This article highlights the technique and its application to numerous studies, ranging from the diffusion of drugs in human skin to chemical warfare agents in barrier materials. In addition to these topics, recent studies with ATR to quantify and model molecular interactions during the diffusion process are reviewed. In the future, the ATR technique may have an impact on a variety of emerging fields in which diffusion in polymers plays an important role, such as fuel cells, membrane separation, sensors, and drug delivery. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2794–2807, 2003     

A two-dimensional infrared correlation spectroscopic study on the thermal degradation of poly(2-hydroxyethyl acrylate)-co-methyl methacrylate/SiO2 nanohybrids

Two-dimensional infrared (2D IR) correlation spectroscopy was applied to study the structural changes occurring in the decomposition of PHEA-co-MMA/SiO₂. Complicated absorption spectral changes were observed in the heating process. 2D IR analysis indicates that during heating, covalent bonds, (Si-O-C), between the polymer and the inorganic moiety were formed, which was the main factor in the improvement in thermal properties of the hybrids such as the decomposition temperatures (T_d). The thermal stability of the hybrids was also studied by solid-state ²⁹Si MAS NMR spectroscopy and TGA tests. Their results complemented each other well.     

Determination of chloride ion in aqueous samples by isotope-dilution Fourier-transform flame infrared emission (ID-FIRE) spectrometry

An isotope dilution method for the determination of chloride ion in aqueous samples is described. The method makes use of the isotopic shift in the rotational lines of the 1–0 band of HCl emitted in the near infrared region of the spectrum by vibrationally excited HCl molecules present in a hydrogen/entrained air flame. Chloride ion in the sample is converted to chlorine gas by electrolysis and swept into a hydrogen/entrained air flame where it is converted into HCl. Because isotope dilution is an absolute method of analysis, matrix effects are minimized, and the chlorine generation step need not be quantitative. With the system described in this paper, samples must contain at least 9 mg of chloride ion per ml, and a 2-ml sample is required. Over the range from 10 to 30 mg Cl⁻ ml⁻¹, the average error was −0.96%, and the average relative standard deviation was 3.3% for seven samples using seven of the more intense lines in the P branch. Compared with standard silver nitrate titrations, the isotope dilution procedure was not affected by such common interferences as bromide ion and iodide ion. The technique was applied to several seawater samples from different regions.     

Thermogravimetric study of polyacrylamide with evolved gas analysis

Dried samples of polyacrylamide in an He atmosphere have been subjected to thermogravimetric analysis in the 30–600°C range, and the evolved gases were monitored by FTIR. Water, ammonia, and small quantities of carbon dioxide are released in the first stages of decomposition (220–340°C), where the polymer chains remain intact and the reaction occurs on the pendant amide groups. In the second stage of decomposition (340–440°C), the majority of the weight loss occurs, and main chain breakdown occurs, releasing carbon dioxide, water, nitrile compounds, and imides. Trapping of the gases in this stage and analysis by GC–FTIR and GC–MS reveals the presence of more than 20 decomposition products, and confirms that a large proportion of these can be assigned to glutarimide and its substituted analogs. Imidization and dehydration reactions on the amide groups, as well as free radical breakdown of the main chains, with inter- and intramolecular hydrogen transfer, can account for many of the products of the decomposition. © 1993 John Wiley & Sons, Inc.