A Quick Method for the Microanalytical Evaluation of the Dissolving Power of Supercritical Gases

A new method of microextraction with supercritical gases involving direct coupling with thin-layer chromatography enables the solubility behavior of a large number of natural products to be investigated in pressure gradients of up to 400 bar. The results are summarized in general rules that enable the extractability to be predicted on the basis of the chemical structure. The substances that can be satisfactorily extracted in supercritical carbon dioxide and nitrous oxide are preferably lipophilic. The extracting capacity of the two gases was compared using alkaloids. In the case of polar compounds such as sugars and amino acids the solubility is so low even at pressures of 2500 bar (less than 10 μg/Nl) that application is not practicable. Quantitative tests of the solubility behavior of model substances in supercritical gases provide a basis for the technical application of the method.     

Physicochemical Principles and Applications of Supercritical Fluid Chromatography (SFC). New analytical methods (19)

In supercritical fluid chromatography (SFC) compressed gases in the region of their critical temperature are used as mobile phases. SFC has important advantages over gas chromatography (GC) for the separation of low-volatile or thermally unstable substances. Like high pressure liquid chromatography (HPLC) and gel chromatography, it is used for various special applications and preparative separations, e.g. in the petroleum industry and in the separation of oligomers. SFC is of great interest in fundamental research on fluid extraction and for the determination of the physicochemical properties of fluid systems. In this contribution the most important physicochemical, methodological, and instrumental principles of SFC are summarized; characteristic physicochemical applications are the determination of capacity ratios, partition coefficients, partial molar volumes, interaction second virial coefficients, and difusion coefficients.     

超临界流体色谱中溶质的保留行为

超临界流体色谱中热力学参数最佳化和动力学最佳化同等重要。溶质的保留行为和物质对的分离受柱固定相和流动相各种参数的影响。在本研究中,使用纯CO_2作为流动相,饱和烃、芳烃、以及它们的硝基取代物作为溶质,对上述影响进行了系统地考察。结果发现影响物质对分离的(以分离系数,α,表示)最主要因素是流体的密度。而温度的影响并不明显。柱固定相的性质也有一定程度的影响。在柱固定相相同的情况下,改变操作参数,溶质峰的洗馏顺序可能出现倒置。表明在超临界流体色谱中流动相溶解能力的重要作用。实验结果为了解和优化超临界流体色谱热力学参数提供了依据。     

Physicochemical Principles of Extraction with Supercritical Gases

The present review considers some physicochemical properties of fluid mixtures that are of importance for fluid extraction and supercitical fluid chromatography (SFC). Firstly, the important types of phase diagrams are treated, the occurrence of solid phases also being considered in some simple cases. Specific examples are given of mixtures of a highly volatile component I (e.g. CO₂, C₂H₆) with a relatively involatile component II (e.g. squalane) of very different molecular size, shape, structure, and/or polarity, and it is shown how the rather complicated types of phase diagrams can be calculated and correlated. The importance of fluid mixtures extends far beyond the fields of science and technology reviewed.     

超临界流体的共溶剂效应和混合流体研究进展

共溶剂的出现极大地拓展了超临界流体的应用范围,推动了超临界流体科学与技术的发展。本文从相行为和分子间相互作用热力学的角度,对相行为测定、量热技术、光谱技术和分子模拟等在超临界流体中共溶剂效应的研究作了综述,主要介绍超临界流体中共溶剂的作用机理和混合流体在临界点附近热力学性质研究,并对其未来发展方向进行了展望。     

超临界流体中CO和H2吸附过程的Monte Carlo模拟

利用Monte Carlo (MC) 方法,研究了一氧化碳和氢气在不同密度正己烷中的等温吸附情况.模型考虑了正己烷密度对一氧化碳和氢气在催化剂表面吸附量与吸附速率的影响.结果表明,主要有三个因素会影响溶质的吸附量:当溶剂密度低于其临界密度时,体系压力是影响溶质吸附量的主要因素；当体系处于超临界区时,超临界溶剂的溶解能力以及溶质和溶剂之间的竞争吸附是影响溶质吸附量的主要因素.在一定范围内增加溶剂的密度（压力）可以提高溶质在催化剂表面的吸附速率.     

Large-Scale Industrial Plant for Extraction with Supercritical Gases

Criteria for the design and construction of plant for obtaining carrier material or extracts are discussed for the example of the extraction of natural products with supercritical carbon dioxide. The parameters to be established and the course of the process in a large-scale plant are indicated. Plant engineering and optimization must be attuned to specific process-technological and construction problems.     

Supercritical fluid chromatography in research laboratories: design, development and implementation of an efficient generic screening for exploiting this technique in the achiral environment

A new strategy for exploiting SFC in the achiral arena has been designed, developed and successfully implemented in our Analytical Technologies laboratories, in support of Drug Discovery. The development of a generic analytical SFC/MS screening protocol, following extensive evaluation of different stationary phase, modifier and gradient elution combinations, has enabled fast analytical method development for structurally diverse compounds within both specialised and high-throughput purification environments. Application of this approach into the daily routine has provided data on a large number and a wide variety of reaction mixtures. The results confirm the scope and generality of the strategy with more than 85% of targets being successfully resolved from their impurities.     

Separation with Supercritical Gases: Practical Applications

Extraction with supercritical gases combines, to a certain extent, the characteristics of both distillation and extraction; the term “destraction” is therefore proposed for this method of separation. The principles of the method are illustrated in this article by a series of color photographs comparing extraction and destraction. Of the practical uses of this new method may be mentioned the separation of cod-liver oil into 50 fractions, each differing in saponification value and iodine number, by means of supercritical ethane and, in particular, the decaffeination of raw coffee with supercritical carbon dioxide.     

超临界流体在有机合成中的应用

超临界化学反应是一种新型的反应体系，本文对超临界流体在有机合成反应中应用的最新进展进行了综述。     

Vibrational Spectroscopy in Supercritical Fluids: From Analysis and Hydrogen Bonding to Polymers and Synthesis

Supercritical fluids are beginning to be used widely in chemistry. Applications range from extraction and chromatography in analytical chemistry to solvents for reaction chemistry and preparation of new materials. Spectroscopic monitoring is important in much of supercritical chemistry, and vibrational spectroscopy is particularly useful in this context because the vibrational spectrum of a given molecule is usually quite sensitive to the environment of that molecule. Thus, vibrational spectra are excellent probes of conditions within the fluid. In this review, we describe a variety of techniques and cells for IR and Raman spectroscopy in supercritical fluids and illustrate the breadth of applications in supercritical fluids. The examples include: the use of supercritical Xe as a spectroscopically transparent solvent for chemistry and for supercritical fluid chromatography with FTIR detection of analytes; Raman spectroscopy as a monitor for gases dissolved in supercritical CO₂; the effect of solvent density on hydrogen bonding in supercritical fluids and the formation of reverse micelles; IR as a monitor for the supercritical impregnation/extraction of polymers and the reactions of organometallic compounds impreganated into polymers; reactions of organometallic compounds in supercritical fluids; and finally, the use of miniature flow reactors for laboratory-scale preparative chemistry. Overall, our aim is to provide a starting point from which individual readers can judge whether such measurements might usefully be applied to their own particular problems.     

超临界流体化学热力学

本文简要介绍了超临界流体的基本概念和性质,评述了化学热力学在超临界萃取、超临界态化学反应、超临界流体制备材料等方面的作用和研究进展,讨论了二氧化碳-离子液体两相体系的热力学行为。     

Fluid Extraction of Hops,Spices, and Tobacco with Supercritical Gases

This report provides an introduction to the principal methods of extraction with supercritical gases, illustrated by the processing of some natural products with carbon dioxide. The combination of pressure and temperature as process parameters makes it possible to vary the solvent power of the medium within certain ranges as desired without having to change the composition of the solvent, as would be necessary in conventional solvent extraction. The problem-free handling of carbon dioxide and also of the products obtained open up possibilities whose development has only just started.     

超临界流体色谱分析番茄红素

以超临界CO2作为流动相，在压力15.0-20.0MPa，温度25－50℃，携带剂乙醇或正己烷的浓度分别为0－30％和0－20％的范围内考察了番茄红素及其氧化产物在C18色谱柱上的保留值的变化规律，确定了最佳的分离条件。对超临界丙烷萃取的番茄红素原料、萃取产物及萃余物进行了定量分析，考察了重复性及平行性。结果表明：在优化条件下，番茄红素的保留时间在3min以内，定量结果的重复性与平行性好。     

Adsorption of Supercritical Fluids

Adsorption isotherms for supercritical fluids are calculated using lattice theory. Results are compared with experimental data for methane on graphon and for carbon dioxide on coal. It is shown that the model reflects the peculiar features in adsorption isotherms of supercritical fluids (in particular, a maximum in the adsorption with increasing pressure). The analysis shows that there is two layer adsorption over a wide range of densities.     

超临界CO2/离子液体体系

超临界CO2和离子液体是两种具有优异性能的绿色化学试剂,本文介绍了将两者结合反应,分离体系的物化性质和多种绿色化学过程。利用超临界CO2可以广泛地萃取离子液体中的不挥发性化合物而不导致离子液体及其中催化剂的流失,在加氢、醛化、甲酰化等反应,分离过程中的应用表明,过程具有很好的反应分离特性和环境友好性,应用前景广阔。     

Chemistry in Supercritical Water

Water is a special liquid —and not only under “normal” conditions. Water in the supercritical state (shaded area in the phase diagram) is distinguished by special properties which are wholly at variance with those of normal water. So far these have usually been exploited for the purification of waste water, for example for the complete oxidation of poorly degradable substances. But what is the potential of supercritical water for synthesis? Answers are provided here on the basis of thermodynamic and kinetic studies as well as with reference to measurements of corrosion.     

超临界流体色谱法分离生育酚同系物

用超临界流体色谱法进行了生育酚异构体的分离研究。在实验温度303．15K～343．15K和压力14～22MPa范围内，考察了ODS柱上温度、压力和密度与容量因子和选择性的关系，得到了生育酚在超临界色谱中的最佳分离条件：温度为343．15K，压力为20MPa，CO2流量750mL/min。