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《Analytical letters》2012,45(9):2009-2024
Abstract Adding additional components to supercritical carbon dioxide in supercritical fluid chromatography can extend or significantly alter the fluid solvating properties. Polar samples which are difficult to be analyzed with pure supercritical CO2 because of their high polarity can be separated by adding polar modifiers to supercritical CO2. In this paper, a new mixing device using a teflon high capacity filter for adding polar modifiers to carbon dioxide mobile phase is introduced. This new mixing device could keep the amount of modifier in the mobile phase constant for a much longer time than a saturator column. The amount of water or methanol dissolved in supercritical CO2 was measured by amperometric microsensor which is made of thin film of perfluorosulfonate ionomer(PFSI). 相似文献
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Rebecca R. Edwards Yingmei Tao Sihua Xu Phillip S. Wells Kwang S. Yun Jon F. Parcher 《Journal of Polymer Science.Polymer Physics》1998,36(14):2537-2549
The effect of dissolved carbon dioxide on the glass transition temperature of a polymer, PMMA, has been investigated using molecular probe chromatography. The probe solute was iso-octane, and the specific retention volumes of this solute in pure PMMA and mixtures of PMMA with CO2 were measured over a temperature range of 0 to 180°C and CO2 pressures from 1 to 75 atm. The amount of CO2 dissolved in the polymer was calculated from a model fit to previously published solubility data determined chromatographically. Classical van't Hoff-type plots were used to determine the glass transition temperature of CO2-impregnated PMMA from low pressure up to 46 atm of CO2. Solvent-induced plasticization was observed with the glass transition temperature decreasing by about 40°C. At some pressures, glass transitions at low temperatures could not be determined from the van't Hoff plots because of the proximity of the polymer glass transition temperature to the gas–liquid transition temperature for CO2. For these pressures, a new method was developed to determine the glass transition composition. The glass transition pressure was then calculated from the measured composition and temperature using an isotherm model. In every case, the glass transition temperature decreased linearly with increasing concentration of CO2 in the polymer. However, at higher compositions, the glass transition pressure decreased with increasing composition and decreasing temperature. The observed retention volume of iso-octane with PMMA in a glassy state was correlated with an adsorption model developed from a theory for liquid–solid chromatography derived by Martire. This model accurately described the observed decrease in retention of iso-octane by adsorption on the surface of glassy PMMA with increasing concentration of CO2 dissolved in the polymer. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2537–2549, 1998 相似文献
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本文对超临界二氧化碳(ScCO2)中进行的聚合反应进行了综述。评述了ScCO2作为聚合反应介质的优点,以及在ScCO2中可进行的聚合反应类型,包括均相聚合、沉淀聚合、分散聚合、乳液及反相乳液聚合、阳离子聚合、开环聚合、熔融态缩聚、溶液-凝胶聚合、聚合物混合合成、链催化转移聚合、氧化-偶合反应聚合、氮氧自由基可控活性聚合、原子转移自由基聚合、可逆加成-断裂链转移、电化学聚合、原子转移聚合与酶催化开环聚合两种活性聚合在ScCO2中同时聚合、二氧化碳作为原料共聚合等。 相似文献
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黄酮类化合物的超临界流体色谱分离 总被引:18,自引:0,他引:18
利用超临界流体色谱成功地分离了黄酮类化合物,研究了流动相组成,柱条件,压力及温度的影响。发现流动相组成是影响色谱分离的最主要因素;其次,色谱柱条件也是影响分离的一个很重要的因素,硅胶基质的键合苯基柱比较适合于极性黄酮类化合物的分离。 相似文献
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柱前手性衍生色谱法拆分DL—氨基酸时流动相的影响 总被引:2,自引:0,他引:2
本文利用邻苯二甲醛和N-乙酰-L-半胱氨酸作柱前手性衍生化试剂,经反相高效液相色谱法拆分DL-氨基酸对映体,研究了流动相组成对出峰顺序和分离效果的影响。 相似文献
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Jun LIU Hong Ping LI Zhi Min LIU Bu Xing HAN* Hai Ke YAN Center for Molecular Science Institute of Chemistry Chinese Academy of Sciences Beijing 《中国化学快报》2001,(5)
Over the past decade there has been a growing interest in using supercritical fluids (SCFs) to promote reactions and to replace hazardous solvents with environmentally benign solvents, such as supercritical CO2 and H2O. Many reactions in SCFs have been studied1, including polymerization in scCO22. It is known that a small change in the pressure near critical point of a fluid causes a significant change in density-dependent properties such as the solubility parameter, viscosity, and dielect… 相似文献
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用超临界二氧化碳重结晶分离菲蒽混合物 总被引:3,自引:0,他引:3
建立了一套以超临界二氧化碳及其改性流体为重结晶溶剂的等压温差超临界流 重结晶实验装置。用色谱保留值法评价了SFR分离菲蒽的试验条件。研究了该实验装置影响重结晶的因素,并对同分异构体型菲蒽模型混合物进行了SFR分离纯化。 相似文献
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Milad Abolhasani Prof. Axel Günther Prof. Eugenia Kumacheva 《Angewandte Chemie (International ed. in English)》2014,53(31):7992-8002
Carbon dioxide (CO2) sequestration, storage and recycling will greatly benefit from comprehensive studies of physical and chemical gas–liquid processes involving CO2. Over the past five years, microfluidics emerged as a valuable tool in CO2‐related research, due to superior mass and heat transfer, reduced axial dispersion, well‐defined gas–liquid interfacial areas and the ability to vary reagent concentrations in a high‐throughput manner. This Minireview highlights recent progress in microfluidic studies of CO2‐related processes, including dissolution of CO2 in physical solvents, CO2 reactions, the utilization of CO2 in materials science, and the use of supercritical CO2 as a “green” solvent. 相似文献
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In recent years, concern about food safety has been growing. The use of food additives in different countries is limited by
specific regulations. Therefore, analytical methods that simultaneously determine artificial sweeteners and preservatives
are advantageous. High performance liquid chromatography has been the most popular choice for the determination of food additives.
In this study, reversed-phase liquid chromatography was developed for the separation of α-aspartame, sodium saccharin, acesulfame-K,
vanillin, sorbic acid and benzoic acid. The effects of the proportion of the organic modifier on the chromatographic separation
were investigated in order to separate these additives. The results showed that optimum chromatographic separation for these
compounds takes place when the acetonitrile content in the mobile phase was 15% containing ammonium acetate buffer (0.005
M). It was concluded that the best separation was obtained with YMC-ODS pack column by using this mobile phase at pH 4.0.
All additives were separated within 40 min. The RP-HPLC-UV method was validated in terms of LOD/LOQ, linearity, recovery and
repeatability. This method was used for the determination of α-aspartame, acesulfame-K and benzoic acid in cola and instant
powder drinks. 相似文献
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Summary A mini extractor of 85 L void volume and a micro extractor of 3–4 L void volume have been coupled directly with a packed column SFC and used under sub- and supercritical conditions. The mini extractor is suitable for holding adsorbates which can be on-line extracted and the extract chromatographed (direct SFE-SFC). The micro extractor can be used for direct sample introduction of liquid and solid materials under SF conditions. Thus any solvent interference with the sample and the chromatographic conditions is excluded. Standard samples of wood tar residue, engine oil, and metal organic compounds have been tested. 相似文献
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设计了一种单阀外循环接口,采用静态溶解度测定方法,联用在线超临界流体色谱,准确测定了芘在超临界二氧化碳中的溶解度.通过釜内磁力搅拌和接口外循环的双重作用,促进芘在超临界二氧化碳中的溶解平衡过程,确保在测定芘溶解度时体系已达到溶解平衡状态,确定了溶解平衡时间,消除了联用体系中因芘的溶解度过高而产生的体系堵塞问题. 相似文献
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Linear solvation energy relationships (LSERs) were used to delineate which specific intermolecular interactions are responsible for changes in retention for a variety of well characterized analytes when acidic and basic additives were used in reversed phase HPLC. The effects of trifluoroacetic acid, triethylamine and a combination of trifluoroacetic acid and triethylamine on the LSERs were compared to those observed in the absence of additives. These effects were examined using four different mobile phase modifiers and five different stationary phases. Trifluoroacetic acid alone and in combination with triethylamine produced LSER regression coefficients nearly identical to those obtained with no additive present in the mobile phase. Triethylamine alone produced different LSER regression coefficients from the other systems unless the mobile phase contained trifluoroethanol as the mobile phase modifier, or the stationary phase consisted of a polymeric support. 相似文献
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Palladium-Catalyzed Addition of Carbon Monoxide and Carbon Tetrachloride to 1-Octene in Supercritical Carbon Dioxide 总被引:1,自引:0,他引:1
The Pd-catalyzed addition of carbon monoxide and carbon tetrachloride to 1-octene gave coadduct [alkyl 2-( 2, 2, 2-trichloroethyl)octanoate] as the major product in supercritical carbon dioxide by using pyridine as the base. It was found that the selectivity and the yield of coadduct were greatly affected by the pressure of carbon dioxide, the reaction temperature and the amounts of alcohol and base used. 相似文献
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采用超临界甲醇处理活性炭,水浸渍制备负载钌炭催化剂,用N2物理吸附、Boehm滴定、X光电子能谱(XPS)和程序升温还原(TPR)等测试技术研究了超临界甲醇处理对活性炭表面结构及表面基团相对含量的影响,并以葡萄糖加氢生产山梨醇为模型反应对钌基催化剂的性能进行了评价。 研究结果表明,超临界甲醇处理活性炭,活性炭的孔结构性能变化不大,但可有效降低活性炭表面含氧酸性基团的含量,使催化剂的还原温度升高,增强了载体和活性组分间的相互作用,有效的提高了钌的分散度,从而提高所负载催化剂的催化活性。 在实验范围内,当超临界甲醇的温度为300 ℃,处理时间为12 h时,在4.0 MPa、120 ℃、葡萄糖的质量分数为50%的反应条件下,催化剂的反应速率(按Ru单位质量计)达到了118.65 mmol/(min·g),是未处理活性炭的1.96倍。 相似文献