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51.
Yu Yang Maya Belghazi Arnaud Lagadec David J. Miller Steven B. Hawthorne 《Journal of chromatography. A》1998,810(1-2):149-159
The intermolecular interactions between organic solutes and sorbent matrices under subcritical water conditions have been investigated at a pressure of 50 bar and temperatures ranging from 50 to 250°C. Both polar and nonpolar organics (chlorophenols, amines, n-alkanes, and polycyclic aromatic hydrocarbons) and five different sorbent matrices (glass beads, alumina, Florisil, silica-bonded C18, and polymeric XAD-4 resins) were used. From the same matrix, the polar solutes always eluted at lower temperatures, while the moderately polar and nonpolar solutes only eluted at higher temperatures. Similar to matrix effects previously observed using supercritical carbon dioxide, the sorbent type greatly influenced the elution efficiency under subcritical water conditions. Lower temperatures are sufficient to elute a particular solute from glass beads, alumina, and Florisil, but higher temperatures (less polar water) are needed to elute the same solute from silica-bonded C18. The highest temperatures were required to elute aromatic organics from XAD-4. These matrix effects demonstrate that, while low temperature water can break inert or dipole interactions between solutes and glass beads, alumina, and Florisil, higher temperature water is required to interrupt the van der Waals attractions between solutes and silica-bonded C18, and even higher temperatures needed to overcome the π-electron interactions between aromatic solutes and XAD-4. 相似文献
52.
53.
GC-MS法测定焦化厂气溶胶中多环芳烃 总被引:2,自引:0,他引:2
利用气相色谱-质谱(GC-MS),电子轰击离子化(EI)法测定焦化厂气溶胶中多环芳烃的含量。超声波抽提气溶胶样品,用GC-MS的选择离子监测(SIM)方式测定EPA提出的优先监测的16种多环芳烃的含量。该法的检出限为0.167pg·m~(-3),PAHs的回收率为85.1%~110.5%,相对标准偏差为4.62%~19.4%。应用该法测定气溶胶中PAHs获得满意的结果。 相似文献
54.
高效石墨浮选剂的合成金婵,薛玉,汪进,刘欣荣,秦英海(哈尔滨工业大学应用化学系哈尔滨150001)(大庆石化总公司大庆)关键词石墨,浮选剂,合成,混合烃由于石墨具有良好的力学性能、导电、高熔点等性质,广泛用于原子能、宇航和民用工业。隐晶质石墨属于微晶... 相似文献
55.
Devendra Kumar Uday Razdan Alka D. Gupta 《Journal of polymer science. Part A, Polymer chemistry》1992,30(7):1477-1487
Various melt-polymerizable bisimido-bisphthalonitrile polymer precursors were synthesized by the reaction of 4-aminophthalonitrile (4-APN) with bis(3,4-dicarboxyphenyl) dimethylsilane dianhydride (SIDA), 4,4′-hexafluoroisopropylidene diphthalic anhydride (6FDA), bis(3,4-dicarboxyphenyl)ether dianhydride (ODPA), and 3,3′, 4,4′-tetracarboxylichenzophen+ne dianhydride (BTDA) in an aprotic solvent. The synthesized monomers showed crystalline melting at 269 and 271°C. Elemental analysis, differential thermal analysis (DTA), infrared (IR), nuclear magnetic resonance (1H-NMR) and mass spectral studies were carried out to characterize the synthesized monomers. Thermogravimetric analysis (TGA) of the synthesized monomers showed their thermal stability at 410–400°C. A detailed study and NMR investigation of the first step of condensation reaction was carried out and indicated the formation of a transient charge transfer complex. Thermal cyclization of the formed intermediate, however, gave the required monomers. A preliminary study demonstrated that melt-polymerization of the synthesized monomers gave thermallystable, tough polymers. 相似文献
56.
An efficient clean-up procedure coupled with a high performance liquid chromatography (HPLC) with on-line electrochemical (EC) reduction and fluorescence detection (FLD) was developed to quantify nitrated polycyclic aromatic hydrocarbons (NPAHs) in the airborne particulate. In this process, NPAHs were extracted ultrasonically followed by analysis by using a reversed phase column with an aqueous eluent containing 70% aqueous acetonitrile and sodium monocholoroacetate as a buffer solution. The extraction efficiencies were above 83% for 1-nitropyrene and 1,3-dinitropyrene (1,3-DNP) 1,6-DNP, and 1,8-DNP, and calibration graphs were linear with very good correlation coefficients (r>0.999) and the detection limits were in the range of 1.0-2.2 pg for dinitropyrenes and nitropyrene. The proposed method provides a relatively simple and convenient procedure for determining the NPAHs samples in airborne particulate. 相似文献
57.
本文综述了目前国际上对铁硫蛋白模型化合物研究的进展情况,介绍了NH---S氢键和芳香环在这些模型化合物及其天然蛋白中的作用。作为铁硫蛋白活性中心的模型,至今已有许多化合物被合成出来,通过这些模型化合物的研究知道,NH---S氢键和芳香环在调控配合物及天然蛋白的氧化还原电位和稳定性方面起着非常重要的作用。另外,作为顺式乌头酸酶、固氮酶等金属酶的模型,已成功地合成了含3Fe4S核以及含钼的铁硫簇合物。 相似文献
58.
The solubilization of benzo[a]pyrene by organic solvents (dioxane, toluene and dichloromethane) and a surfactant (Triton X-100) was investigated. These media were successfully used for the determination of benzo[a]pyrene using fluorescence detection, with excellent limits of detection and large linear analytical ranges. Benzo[a]pyrene was detected in coal washing waters using liquid chromatography with fluorescence detection. The stability of this compound in dioxane was also examined. 相似文献
59.
Shigeru Matsuo Tomoyoshi Murakami Ryuichi Takasawa 《Journal of polymer science. Part A, Polymer chemistry》1993,31(13):3439-3446
Crystalline poly(arylene ether nitrile) could be prepared by the polycondensation of 2,6-dihalobenzonitrile with resorcinol at 200°C in N-methylpyrrolidone in the presence of sodium carbonate. A reaction temperature of at least 200°C was necessary to attain high molecular weight polymer. Spectral data indicated that the polymer had the structure of a poly(meta-phenylene ether) with pendent nitrile groups on every other phenylene unit. Despite this structure, the crystallinity and the crystallization rate of the polymer were greater than those of the corresponding polymer with a para-linked structure. The glass transition temperature and the melting temperature of the polymer were almost the same as those of poly(etheretherketone) (PEEKTM). A series of other new poly(arylene ether nitriles) were also examined. The polymers derived from 4,4′-biphenol, dihydroxytetra-phenylmethane, dihydroxydiphenylsulfone, and 1,5-isoquinolinediol had high glass transition temperatures. The poly(arylene ether nitriles) exhibited excellent tensile strength compared with the corresponding ketone- or sulfone-containing polymers. Comparing the three different kinds of polymers containing the same bisphenol units, the order of glass transition temperature was found to be sulfone- > nitrile- > ketone-containing polymers, while the order of tensile strength was nitrile- > ketone- > sulfone-containing polymers. The excellent mechanical properties are attributable to dipole-dipole interactions of nitrile groups. © 1993 John Wiley & Sons, Inc. 相似文献
60.
Marianne Baudler 《Angewandte Chemie (International ed. in English)》1982,21(7):492-512
Up to about 15 years ago compounds with a skeleton of phosphorus chains or rings were regarded as “exotic” in the field of nonmetal chemistry. Aside from a number of examples of molecules with two P atoms directly bonded to each other and a few sporadically discovered monocyclic ring compounds, only solids of undefined composition and structure were known. Since then the state of our knowledge in this sector has made considerable progress: between PH3 and its derivatives on the one hand, and the high-molecular modifications of elementary phosphorus on the other, an unexpected variety of well defined compounds have been discovered, showing many similarities to the analogous compounds of carbon. However, surprises can still occur even with “small” phosphorus-containing molecules, as shown by the likewise recently discovered field of phosphorus three-membered ring compounds. 相似文献