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991.
An automated spray-and-trap (ST) chromatographic system was constructed for fast and efficient extraction of volatile organic compounds (VOCs) in aqueous samples with the capability to be deployed in the field for unattended continuous monitoring of surface or ground water. This system was built upon a commercial gas chromatograph with full automation capability using self-developed hardware and software. For sample analysis, fine droplets of the aqueous solution were generated in the extraction chamber by pressure expansion of a clean air stream through a spray nozzle. A portion of the VOCs distributed into the gas phase was retained by a multi-sorbent micro-trap kept at ambient temperature. Flash heating of the sorbent trap desorbed the enriched VOCs onto the gas chromatography (GC) with flame ionization detection (FID) for hydrocarbons or electron-capture detection (ECD) for halocarbons. In order to validate the performance of the ST method. it was compared with a more conventional method, i.e., a purge-and-trap (PT), by analyzing a serious of standard solutions containing benzene, toluene, ethylene. and o-, m-xylenes. Using a purge-and-trap method as a reference for complete extraction, the ST method showed less sensitivity. Extraction recoveries are in consistent with Henry's law constants. To test response time the ST-GC-ECD was periodically switched between tap and underground waters. Negligible carry-over of halogenated species and reproducibility better than 2% relative standard deviation (R.S.D.) can be achieved regardless of large concentration difference between the two sources, thus demonstrating applicability of the ST system for on-site monitoring. 相似文献
992.
Yang X Fu YJ Wang XB Slavícek P Mucha M Jungwirth P Wang LS 《Journal of the American Chemical Society》2004,126(3):876-883
The microsolvation of the suberate dianion, -O2C(CH2)6CO2-, with two separate charge centers was studied by photoelectron spectroscopy and molecular dynamics simulation one solvent molecule at a time for up to 20 waters. It is shown that the two negative charges are solvated in the linear suberate alternately. As the solvent number increases, the negative charges are screened and a conformation change occurs at 16 waters, where the cooperative hydrogen bonding of water is large enough to overcome the Coulomb repulsion and pull the two negative charges closer through a water bridge. This conformation change, revealed both from the experiment and from the simulation, is a manifestation of the hydrophilic and hydrophobic forces at the molecular level. 相似文献
993.
994.
Yuming Dong Yuqiang Ding Weifu Dong Cheng Yang Xuefeng Liu Ye Fan Jing Wang Qingwei Pan 《大学化学》1986,35(10):71-76
Based on the development prospect of cosmetics industry, the advantage of light industry characteristic and the foundation of applied chemistry in Jiangnan University, a systematic upgrading of applied chemistry was carried out through "emerging engineering education (3E)" project "upgrade and practice of chemistry-related majors of local and/or trade university responding to the social developments" supported by the Ministry of Education. On the basis of investigation and analysis, the orientation and training goal of applied chemistry were updated first, and then the curriculum system was determined and the curriculum construction is strengthened, so as to achieve more distinctive characteristics, more solid foundation and more comprehensive quality. In view of the new requirements of the 3E for talent training, some practices have been formed in the aspects of multi-disciplinary integration, multi-angle coordination and close integration to industry. Contributing the development of cosmetics industry and seizing the commanding point of science and technology from the perspective of talent training, will play a unique role in human social progress. 相似文献
995.
996.
“逐步偶联聚合反应”在研制有序交联高分子及复合物中的应用 总被引:3,自引:0,他引:3
用“逐步偶联聚合反应”这一新的合成方法可制备不同等级的微观结构可控的有序交联网状高分子,包括可溶性的一维梯形或管状高分子、不溶性的二维或三维筛板状高分子,新型的反应性梯形聚硅氧烷包括氢梯、乙烯基或丙烯基梯、乙氧基梯及其共聚物是功能性梯形高分子的前体,由此衍生出“鱼骨形”和“划艇形”液晶和非线性高分子、盘状金属络合物液晶高分子以及管状聚硅氧烷。对功能化梯形降硅氧烷进行了有趣的应用探索,包括用于稳定液 相似文献
997.
病态分析体系有偏估计的研究 总被引:3,自引:0,他引:3
运用广义岭估计和Liukejian提出的有偏估计,对病态分析体系进行了数值模拟和实际光度测定,结果表明,广义岭估计显优于最小二乘估计,Liukejian法有功效,可和为解析病态分析体系的化学计量学方法。 相似文献
998.
聚全氟丙醚油是一种新型的性能独特的润滑油。本实验采用~(19)F-NMR波谱法,结合~1H-NMR和MS法,较详细地研究了油品微观结构。由谱线的化学位移和强度归纳出不同链节结构的分布,同时阐明了端基结构。 相似文献
999.
1000.
Nd—Al双金属活性体的组成及其对共轭双烯烃的聚合 总被引:1,自引:0,他引:1
稀土Ziegler-Natta催化剂活性体对双烯烃配位聚合的研究已有很多报道。作者曾从NdCl_3·3P_(350)~(**)-Al(i-Bu)_3体系分离出Nd-Al双金属活性体。本文从NdCl_3·3P_(350)-HAl(i-Bu)_2和Al(C_2H_5)_3反应体系中分离出一系列Nd-Al双金属活性体,用元素分析方法研究了这些活性体的组成,并综合考察了在无助催化剂AlR_3存在下从不同烷基铝获得的活性体本身对共轭双烯烃的定向聚合能力。 单体、溶剂、HAl(i-Bu)_2、Al(C_2H_5)_5及活性体的合成,聚合方法,聚合物表征均按文献[4]。 相似文献