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991.
An effective method was developed to use an enzyme in ionic liquids; the asymmetric reduction of ketones by Geotrichum candidum in ionic liquids proceeded smoothly with excellent enantioselectivity when the cell was immobilized on water-absorbing polymer containing water, while the reaction without the polymer did not proceed. 相似文献
992.
Shu-Liang Zang Qing-Guo Zhang Ming Huang Bin Wang Jia-Zhen Yang 《Fluid Phase Equilibria》2005,230(1-2):192-196
This paper reports that an ionic liquid (IL) has been prepared by directly mixing InCl3 and 1-methyl-3-ethylimidazolium chloride (EMIC) with molar ratio 1/1 under dry argon atmosphere. The densities, and surface tension of the pure IL were determined at temperature range of 293.15 to 343.15 ± 0.1 K. The volumetric properties and the properties of surface for ionic liquid based on group III were discussed by Glasser's theory and Yang's interstice model. 相似文献
993.
Purification of plasmid DNA vectors by aqueous two-phase extraction and hydrophobic interaction chromatography 总被引:4,自引:0,他引:4
The current study explores the possibility of using a polyethyleneglycol(PEG)-ammonium sulphate aqueous two-phase system (ATPS) as an early step in a process for the purification of a model 6.1 kbp plasmid DNA (pDNA) vector. Neutralised alkaline lysates were fed directly to ATPS. Conditions were selected to direct pDNA towards the salt-rich bottom phase, so that this stream could be subsequently processed by hydrophobic interaction chromatography (HIC). Screening of the best conditions for ATPS extraction was performed using three PEG molecular weights (300, 400 and 600) and varying the tie-line length, phase volume ratio and lysate load. For a 20% (w/w) lysate load, the best results were obtained with PEG 600 using the shortest tie-line (38.16%, w/w). By further manipulating the system composition along this tie-line in order to obtain a top/bottom phase volume ratio of 9.3 (35%, w/w PEG 600, 6%, w/w NH4)2 SO4), it was possible to recover 100% of pDNA in the bottom phase with a three-fold increase in concentration. Further increase in the lysate load up to 40% (w/w) with this system resulted in a eight-fold increase in pDNA concentration, but with a yield loss of 15%. The ATPS extraction was integrated with HIC and the overall process compared with a previously defined process that uses sequential precipitations with iso-propanol and ammonium sulphate prior to HIC. Although the final yield is lower in the ATPS-based process the purity grade of the final pDNA product is higher. This shows that it is possible to substitute the time-consuming two-step precipitation procedure by a simple ATPS extraction. 相似文献
994.
Attila R. Imre W. Alexander Van Hook Bong Ho Chang Young Chan Bae 《Monatshefte für Chemie / Chemical Monthly》2003,134(12):1529-1539
Summary. Upper critical solution temperatures (UCSTs) for liquid–liquid demixing in a set of mixtures of linear alkanes (pentane (N
1=5) to pentacontane (N
1=50)) with an oligostyrene (1241amu, N
2=12) are reported. We find strong correlation between the Hildebrand solubility parameters of the alkanes and the UCST. Correlations are developed which enable predictions concerning the miscibility of mixtures of compounds with longer chains. 相似文献
995.
M. Jochum R. Bakry I. Wartusch C. W. Huck H. Engelhardt G. K. Bonn 《Chromatographia》2002,56(5-6):263-268
Summary This paper reports on the use of a polymer-based, strong anion-exchange stationary phase for rapid, selective and sensitive
analysis of physiological important mono-, di- and oligosaccharides by high-performance anion-exchange chromatography (HPAEC)
with pulsed amperometric detection (PAD) under alkaline conditions. The adsorbent was obtained by direct nitration of 3 and
5 μm, spherical non-porous highly cross-linked, styrene-divinylbenzene copolymer (PS-DVB) beads, followed by reduction of
superficially introduced nitro groups with nascent hydrogen and quaternization of the resultant amino groups with iodomethane.
Extended exposure to high pressure and strong alkaline conditions did not have any untoward effect on mechanical stability
and chromatographic performance. A comparison of the 3 and 5 μm beads showed, that the synthesized 3 μm highly cross-linked
PS-DVB particles are the preferred phases for the separation of monosaccharides and the 5 μm particles are preferable for
the separation of oligosaccharides. To demonstrate the suitability for the analysis of complex samples, the optimized and
validated system was used for the determination of glucose, fructose and sucrose in apple juice and other soft drinks such
as Coca Cola. Finally, analysis within a few minutes without sample pretreatment down to a lower limit of detection of 0.174–0.504
μg mL−1 at a linearity with R2>0.994 and a repooducibility higher than 98% further confirmed the efficiency of these polymeric sorbents. 相似文献
996.
Inversion of the temperature coefficient of internal pressure in liquid phase systems is considered. Both temperature and concentration inversions of the coefficient are shown to be possible. Details of the temperature inversion are discussed. This type of inversion is characteristic of only associated hydrogen-bonded liquids and is due to weaker association of molecules. 相似文献
997.
J. Vijande J. L. Legido T. P. Iglesias E. Lpez J. Fernndez 《Fluid Phase Equilibria》1995,110(1-2):53-71
In this work we have estimated the structural and interactional parameters of the ether- group for the group-contribution model of Nitta-Chao using a extensive experimental database of thermodynamic properties of ethers (monoethers, polyethers and acetals) and ether + n-alkane and ether + ether mixtures. The results obtained by Nitta-Chao model with this parameters get closer to the experimental values than those obtained with parameters of Eckart et al. (1986). The thermodynamic properties obtained by the Nitta-Chao model with old and new parameters were compared to predictions by other models such as Flory (1965) theory, DISQUAC (Kehiaian, 1977) model and UNIFAC model (versions of Dang and Tassios, 1986, and Larsen et al., 1987). 相似文献
998.
Summary A reversed-phase HPLC method has been developed for the urinary determination of mutagenic 2,4- and 2,6-toluendiamines. These
amines are degradation products of polyurethane, a material used to cover textured silicone breast implants. FMOC-Cl was used
as fluorescent derivatising agent in order to obtain a limit of detection of 15 ng/ml in urine. Pre-treatment of urine samples
was by liquid/liquid extraction and urine specimens of patients after surgury were analysed. 相似文献
999.
胆甾型苯并-15-冠-5(简称CH-B-15-C-5)在不同温度范围内的相态不同,在同一温 度范围内因处理方式不同而物性亦相去甚远,用其作成的GC固定相兼具气固色谱(GSC)、 普通气液色谱(GLC)和冠醚液晶气液色谱(CL-GLC)多种功能。用该固定相在不同条件下对 乳酸和乳酸乙酯光学异构体混合物的分高效果进行了比较研究,并探讨了手性拆分机理。 相似文献
1000.
The use of inductively coupled plasma mass spectrometry (ICP-MS) coupled with separation techniques for the purpose of elemental speciation has recently gained a lot of attention. Much of this is due to ever improving separation capabilities of Chromatographic techniques, the high sensitivity of ICP-MS, and the continuing development of better interface techniques. Additionally, there is a growing awareness of the need to monitor various species of an analyte, rather than just total analyte concentrations, due to their often varying natures. For the sake of learning from different elemental speciation approaches, this review brings together some selected types of elemental speciation which have been recently seen in literature. These include separations using various forms of liquid chromatography, such as reversed phase, reversed phase ion pairing, micelle, ion exchange, and size exclusion. Elemental speciation employing gas Chromatographie separations and supercritical fluid separations are discussed as well as elemental speciation using capillary electrophoresis. 相似文献