SYNTHESIS, CROSSLINKING MECHANISM AND PROPERTIES OF A POLYACRYLATE/POLYURETHANE COMPOSITE COATING

A polyacrylate/polyurethane (P(A) / P(U)) composite coating has been prepared bycrosslinking an acetoacetylated polyacrylate with a vinylic group terminated polyurethaneat room temperature. A model Michael reaction between ethyl acetoacetate (EAA) andmethyl acrylate (MA) was designed to study the crosslinking mechanism. It was foundthat the two active hydrogen atoms in acetoacetyl group can both add to vinylic groupsand the yield of mono- and bis-adducts are much affected by the molar ratio of acetoacetylto vinylic groups. Higher crosslinking degree and better properties could be obtained withdecreasing the molar ratio of the two active groups from 1/1 to 0.6/1 in the compositecoatings.     

动态液相微萃取GC/MS-SIM方法检验毛发中的苯丙胺类毒品

建立了动态液相微萃取GC/MS-SIM方法检测毛发中4种苯丙胺类毒品的方法.毛发样品首先用1 mol/L NaOH溶液消解,然后用50μL氯仿涡旋提取1min,离心后用注射器直接抽取有机相,提取液进行GC/MS-SIM方法检测.毛发样品的测出限(S/N=3)分别为苯丙胺1 ng/mg,甲基苯丙胺、3、4-(亚甲二氧基)苯丙胺、3、4(亚甲二氧基)-甲基苯丙胺500 pg/mg.在毛发中添加上述4种苯丙胺毒品的质量分数为5 ng/mg时,5次测定的RSD分别为苯丙胺8.3%,甲基苯丙胺8.2%,3、4-(亚甲二氧基)苯丙胺2.0%,3、4(亚甲二氧基)2.7%.该方法可用于毛发中低含量苯丙胺类毒品的分析.     

Solid-phase microextraction for qualitative and quantitative determination of migrated degradation products of antioxidants in an organic aqueous solution

Low molecular weight aromatic substances may migrate out from plastic packaging to their contents, especially if they consist of organic aqueous solutions or oils. It is, therefore, extremely important to be able to identify and quantify any migrated substances in such solutions, even at very low concentrations. We have in this work investigated and evaluated the use of solid-phase microextraction for the specific task of extraction from an organic aqueous solution such as a simulated pharmaceutical solution consisting of 10 vol.% ethanol in water. The goal was furthermore to investigate the possibility of simultaneously identifying and quantifying the substances in spite of differences in their chemical structures. Methods were developed and evaluated for extraction both with direct sampling and with headspace sampling. Difficulties appeared due to the ethanol in the solution and the minute amounts of substances present. We have shown that a simultaneous quantification of migrated low molecular weight degradation products of antioxidants using only one fibre is possible if the extraction method and temperature are adjusted in relation to the concentration levels of the analytes. Comparions were made with solid-phase extraction.     

Applicability of headspace solid-phase microextraction to the determination of multi-class pesticides in waters

The applicability of headspace solid-phase microextraction (HS-SPME) to pesticide determination in water samples was demonstrated by evaluating the effects of temperature on the extraction of the pesticides. The evaluations were performed using an automated system with a heating module. The 174 pesticides that are detectable with gas chromatograph were selected objectively and impartially based on their physical properties: vapor pressure and partition coefficient between octanol and water. Of the 174 pesticides, 158 (90% of tested) were extracted with a polyacrylate-coated fiber between 30 and 100 degrees C and were determined with gas chromatograph-mass spectrometry. The extraction-temperature profiles of the 158 extracted pesticides were obtained to evaluate the effects of temperature on the extraction of pesticides. The pesticides were classified into four groups according to the shape of their extraction-temperature profiles. The line of demarcation between extractable pesticides and non-extractable pesticides could be drawn in the physical property diagram (a double logarithmic plot of their vapor pressure and partition coefficient between octanol and water). The plot also revealed relationships between classified extraction features and their physical properties. The new method for multi residue screening in which the analytes were categorized into sub-groups based on extraction temperature was developed. In order to evaluate the quantitivity of the developed method, the 45 pesticides were chosen among the pesticides that are typically monitored in waters. Linear response data for 40 of the 45 was obtained in the concentration range below 5 microg/l with correlation coefficients ranging between 0.979 and 0.999. The other five pesticides had poor responses. Relative standard deviations at the concentration of the lowest standard solution for each calibration curve of the pesticides ranged from 3.6 to 18%. The value of 0.01 microg/l in the limits of detection for 17 pesticides was achieved only under the approximate conditions for screening, not under the individually optimized conditions for each pesticide. Recoveries of tested pesticides in actual matrices were essentially in agreement with those obtained by solid-phase extraction.     

微波诱导等离子体热解法合成碳膜包裹的TiO2纳米微晶

微波诱导等离子体热解法合成碳膜包裹的ＴｉＯ２纳米微晶刘洪波（广东石油化工高等专科学校广东茂名５２５０００）洪品杰戴树珊（云南大学化学系云南昆明６５００９１）关键词微波诱导等离子体包裹碳膜ＴｉＯ２纳米微晶中图分类号Ｏ６１４．４１１近年来，对碳膜包裹型材...     

分子印迹技术在样品前处理中的应用

分子印迹聚合物具有选择性高、稳定性好及制备简单的特点,可用于生物、医药、环境样品等复杂基体中痕量分析物的高选择性分离与富集,因此在样品前处理中的应用特别引人关注.本文介绍了分子印迹技术的基本原理,综述了分子印迹技术在样品前处理中应用的研究进展.     

Determination of L-Dopa and L-Dopamine in Aqueous Solutions Using In-Loop SPME Coupled with LC

A new in-loop solid-phase microextraction (in-loop-SPME) technique, based on an aluminum capillary tube coupled to HPLC, is described for on-line isolation, concentration, and analysis of analytes from aqueous samples. L-Dopa and L-dopamine, in aqueous solutions, were selected as model compounds. The main conditions affecting extraction of the analytes from aqueous samples, desorption, injection, and chromatographic separation were investigated. The method is simple and reproducible. Using the proposed method, reliable determination of L-dopa and L-dopamine at parts-per-billion concentrations was achieved. The calibration plots were linear in the range of 2.5–1500 ng mL⁻¹ with correlation coefficients of 0.999 and 0.998 for L-dopa and L-dopamine, respectively. The detection limits were 0.5–1 ng mL⁻¹ with a relative standard deviation less than 4.1%. Concentration factors more than 100-fold were obtained for these compounds.     

Preparation of TiO2 Sol Using TiCl4 as a Precursor

A titanium dioxide sol with narrow particle size distribution was synthesized using TiCl₄ as the starting material. The sol was prepared by a process where HCl was added to a gel of hydrated titanium oxide to dissolve it. The resulting aqueous titanic acid solution was heated to form titanium dioxide sol. The effects of preparation parameters were investigated. TiCl₄ was slowly added to distilled water at 5°C. Aqueous solution of sodium hydroxide was added to adjust the pH of the system to 8–12. After aging for a period of time, the peptized sol was filtered and sufficiently washed. The filtered cake was repulped in water. Hydrochloric acid was slowly added to the solution with stirring. After condensation reaction and crystallization, a transparent sol with suspended TiO₂ was formed. XRD results show that the crystalline phase was anatase. The suspended TiO₂ particles were rhombus primary particles with the major axis ca. 20 nm and the minor axis ca. 5 nm. The TiO₂ particles prepared at pH 8 had the largest surface area of 141 cm³/g and it was microporous. The compositions of the solution which yielded the smallest suspended TiO₂ particles were TiO₂:HCl (35% HCl) = 1:1 (molar ratio), concentration of TiO₂ = 10%. Hydroxypropyl cellulose with viscosity of 150–400 cps was added as a dispersant. The sol was excellent in dispersibility and long-term stability. Transparent thin films could be obtained through dip-coating glass substrate in the sol. The dip-coating on glass can be less than three times to have one monolayer TiO₂. The transparent TiO₂ thin film had strong hydrophilicity after being illuminated by UV light.     

Li_3PO_4包覆LiMn_2O_4正极材料的结构表征和电化学性能

采用共沉淀法在尖晶石LiMn2O4颗粒表面包覆Li3PO4.XRD、SEM研究结果表明,包覆后的材料仍为尖晶石结构,粒径均匀.电化学性能测试表明,Li3PO4包覆层的存在,减少了正极材料与电解液的直接接触,抑制了高温下电解液对LiMn2O4材料的侵蚀,从而有效改善了高温下材料的循环性能.在40℃时,包覆样品的比容量衰减率都低于未包覆样品,其中包覆1%Li3PO4的样品的初始比容量为110.4mAh/g,50次循环后比容量为84.1mAh/g.     

Dynamically coating the capillary with 1-alkyl-3-methylimidazolium-based ionic liquids for separation of basic proteins by capillary electrophoresis

Ionic substances with melting points close to room temperature are referred to as ionic liquids. Because ionic liquids are environmentally benign and are good solvents for a wide range of both organic and inorganic materials, interest for their potential uses in different chemical processes is increasing. In this paper, a capillary electrophoretic method for the analysis of basic proteins including lysozyme, cytochrome c, trypsinoge, and α-chymotyypsinogen A is reported. The method, in which 1-alkyl-3-methylimidazolium-based ionic liquids are used as the running electrolytes, leads to a surface charge reversal on the capillary wall. The effects of the alkyl group, imidazolium counterion, and the concentration of the ionic liquids were discussed. The optimum buffer system was a 90 mM 1-ethyl-3-methylimidazolium tetrafluoroborate (1E-3MI-TFB) solution. The applied voltage was −15 kV and detection was performed by monitoring absorbance at 240 nm. Baseline separation, high efficiencies, and symmetrical peaks of four proteins were obtained. The R.S.D. values of migration times and peak areas were <0.68 and <3.0%, respectively. The separation mechanism seems to involve association between the imidazolium cations and the proteins.