Cure reaction and phase behavior of liquid crystalline epoxides-anhydride systems

A series of novel liquid crystalline epoxides with lateral substituents were cured with anhydrides and the cure kinetics was investigated by non-isothermal DSC technique. The results showed that the lengths of lateral substituents have great effect on the value of Ea. The curing reaction became less active, when the liquid crystalline epoxides have long lateral substituents and were controlled by diffusion at the late stage of cure. A nematic structure was observed by POM and XRD.     

Gas Chromatographic Method for Routine Determination of Oleanolic and Ursolic Acids in Medicinal Plants

Summary A rapid and simple gas chromatographic method has been established for routine analysis of free oleanolic and ursolic acids in dried samples of medicinal herbs. Soxhlet extraction of triterpenes was followed by solid-phase extraction (SPE). Amounts of the compounds were measured by gas chromatography after silylation of the purified samples. Experiments were performed to establish the optimum conditions (e.g. solvent, and mode and duration of extraction) for calibration curve linearity, sensitivity, reproducibility, and recovery. The conditions used for derivatization and gas chromatographic analysis resulted in an improvement on literature data. The method devised enables accurate routine measurement of many samples in quite a short time (e.g. for chemotaxonomical screening, or quality control of herbal drugs). The practical application of the method was illustrated on five Lamiaceae species.     

一个简单的能呈现二分岔现象的双分子反应模型

二分岔现象(pitchfork bifurcation)是非平衡非线性动力系统中最典型和最简单的分岔现象.1972年Schlogl提出了如下一个化学反应模型: A+2x?3X,X?B (1)假定组份A和B的浓度可由外界控制为恒定,在某些条件下该模型可呈现出二分岔现象.自那以后,Schlogl模型已成为人们研究非平衡相变时最广泛采用的理论模型,该模型对推动非平衡非线性现象的研究起了十分重要的作用.但从物理-化学的角度来看,该模型存在着如下一些问题:首先该模型涉及一个三分子自催化反应步骤,这种反应步骤在现实反应系统     

ICP-AES detection of silicon carbide impurities volatilized in a graphite furnace with the use of carbon tetrachloride vapour

The analytical capability of high-temperature halogenation with carbon tetrachloride vapour in a graphite furnace was investigated for silicon carbide powder with known chemical composition and particle size. Intensity vs heating time curves were determined for analytical lines of Al, B, Ba, Ca, Cr, Cu, Fe, Mg, Mn, Ti, V and Si constituents, volatilized with and without the presence of CCl₄ vapour in the furnace atmosphere. Igniting 10 mg SiC at 2100 °C for 60 s in chlorinating atmosphere, the evaporated fraction of most of the constituents was higher than 90% (for Al about 50%). The line intensity vs sample mass (4–26 mg) relationships were linear for all impurities studied, while the intensity of silicon line showed a relatively small change with the sample mass. BEC (background equivalent concentration) values for this solid sampling technique (10 mg loaded sample) were 2–20 fold lower than those calculated for the conventional solution sample introduction method.     

析相光度法测定铜（Ⅱ）的研究

本文研究了Ｃｕ（Ⅱ）－ＰＥＧ（聚乙二醇－２０００）－Ｚｉｎｃｏｎ（锌试剂）－（ＮＨ４）２ＳＯ４体系的析相光度法并应用于测定Ｃｕ（Ⅱ）。最宜酸度为ｐＨ５．５～８．５（ＫＨ２ＰＯ４－Ｋ２ＨＰＯ４）缓冲溶液）其络合物的最大吸收位于６１０ｎｍ，表观摩尔吸光系数为４．０×１０＾４Ｌ．ｍｏｌ＾－１．ｃｍ＾－１，Ｃｕ（Ⅱ）浓度在０～１．５ｍｇ／Ｌ范围内服从比尔定律，铜与Ｚｉｎｃｏｎ形式组成为１：２的稳定的蓝色络     

Mercury extraction by ionic liquids: temperature and alkyl chain length effect

The preliminary results described here show the complete transfer of Hg(II) ions, in the absence of a chelating agent in 1-alkyl-3-methylimidazolium hexafluorophosphate ionic liquids; the lag time required to gain the quantitative metal ion partition turned out to be strongly dependent both on alkyl chain length on the imidazolium ring and on the working temperature.     

在线萃取流动注射分光光度法测定二羟基苯磺酸钙中微量对苯二酚

用在线萃取-流动注射分光光度法(FISP)测定了作为杂质与2,5-二羟基苯磺酸钙共存的对苯二酚。专门设计并制作了与流动注射分光光度测定单元组合在一起的在线萃取流路,对苯二酚用乙醚萃取进入有机相并在此相中于其吸收峰297.5 nm波长处测定其吸光度,通过萃取基体成分,即2,5-二羟基苯磺酸钙的干扰,由于其在乙醚中不溶解而得以消除。对苯二酚的吸光度与其相应浓度在3.5×10-6~5.0×10-4mol.L-1之间呈线性关系,相关系数达0.999 4。该方法的检出限为2.53×10-6mol.L-1。应用此方法分析了来自不同批次的3个试样,所得结果的RSD在0.69%~1.65%之间,且其值与药典法所测得结果相符。     

Synthesis and electrochemical properties of spinel LiMn2O4 prepared by the rheological phase method

Pure-phase and well-crystallized spinel LiMn₂O₄ powders were successfully synthesized by a simple rheological phase method. The thermal behavior and structure properties of the powders prepared by the rheological phase method compared with the solid-state reaction were investigated by thermogravimetry, powder X-ray diffraction , scanning electron microscopy and transmission electron microscopy. According to the results of the electrochemical tests, it is obvious that the sample resulting from the rheological phase method shows higher discharge capacity and better cycling stability than one formed in the solid-state reaction. The cyclic voltammogram and columbic efficiency curves also confirm that the product by the rheological phase method has a good cycling performance due to its fine cubic spinel structure and morphology.     

Preparation of pyrenebutyric acid-modified magnesia-zirconia stationary phases using phosphonate as spacers and their application to the separation of fullerenes

A novel method was proposed for the preparation of pyrenebutyric acid-modified magnesia-zirconia stationary phases. Pyrenebutyric acid was grafted to magnesia-zirconia composites with different pore sizes via the sodium salt of cis-(3-methyloxiranyl)phosphonic acid (fosfomycin) as spacers. Aminated fosfomycin was first absorbed onto the surface of magnesia-zirconia composites during the preliminary step to provide amino and hydroxy reactive sites. And then the pyrenebutyric acid was covalently attached to the amine or hydroxyl groups via amide or ester bonds. The resulting stationary phases were characterized by elemental analysis, diffused reflectance FT-IR, nitrogen adsorption analysis and ¹³C solid state NMR spectra. The HPLC separation of fullerenes on the new stationary phases with different pore sizes was also investigated. The chromatographic performance showed a dependence on the pore size of the magnesia-zirconia matrix. Little retention of fullerenes was observed on the stationary phase with pore sizes about 4.5 nm. However, on the modified magnesia-zirconia with pore sizes about 10 nm, selectivity factors (α) for C₇₀/C₆₀ separation were determined to be 1.76, 2.29, 2.41, 3.10, with carbon disulfide, chlorobenzene, xylene and toluene as mobile phases, respectively. And the high solubility of fullerenes in these solvents dramatically increased the overall potential with regard to preparative fullerene purification. Among the reported stationary phases with pyrene ligands, the pyrenebutyric acid-modified magnesia-zirconia (PYB-F-(ZrO₂-MgO)) with larger pore sizes exhibited the best selectivity for fullerenes. The thermodynamic and kinetic behavior of fullerenes was also examined.     

Ce0.6Zr0.35Y0.05O2和Pr0.6Zr0.35Y0.05O2催化剂表面上CO氧化和18O-16O交换反应的研究

测定了在Ce0.6Zr0.4O2,Ce0.6Zr0.35Y0.05O2,Pr0.6Zr0.4O2和Pr0.6Zr0.35Y0.05O2 (分别表示为CZ,CYZ,PZ和PYZ)样品表面上的CO氧化反应和18O-16O 同位素交换反应.结果表明: 在CZ和PZ系列固熔中掺杂Y3 离子可以改善晶格氧的迁移速度;PZ和PZY的晶格氧比CZ 和CZY 的晶格氧具有更高的氧化反应活性.其原因是将Y3 掺杂到Ce0.6Zr0.4O2 或Pr0.6Zr0.4O2晶格中,增加了样品的氧空位浓度,从而提高了晶格氧的迁移性质,而PrOx比CeO2具有更低温度的氧化还原性质,因此PZ和PZY的晶格氧比CZ 和CZY 的晶格氧具有更高的氧化反应活性.