Preparative supercritical carbon dioxide

SFC provides complementary quantitative data to the structural information afforded by mass spectrometry. Thermally label materials such as isocyanates can be easily analyzed with minimal sample preparation. Supercritical carbon dioxide is nontoxic and can be obtained in high purity as measured by FID. The easy coupling of SFE with SFC makes the selective isolation and quantification of targeted analytes possible. Furthermore, we are in an age of increased environmental awareness. Solvent disposal is discouraged and has become very expensive. The waste disposal costs associated with supercritical carbon dioxide are negligible when compared to the solvent disposal costs generated by traditional Soxhlet methods. 

Natural Products. Various methods have been and continue to be employed to obtain useful materials from various parts of plants. Essences from plants are obtained by distillation (often with steam), direct expression (pressing), collection of exudates, enfleurage (extraction with fats or oils), and solvent extraction. Solvents used include typical chemical solvents such as alcohols and hydrocarbons. Liquid (supercritical) carbon dioxide has come into commercial use in the 1990s as an extractant to produce perfume materials. The principal forms of natural perfume ingredients are defined as follows the methods used to prepare them are described in somewhat general terms because they vary for each product and suppHer. This is a part of the industry that is governed as much by art as by science. 

Attention should be drawn to a very interesting possibility, viz subjecting drugs before their use as teas to pressure, followed by rapid release of the pressure (so-called PEX procedure), in order to achieve a kind of opening up and thereby improving the liberation of many constituents during the preparation of the tea. The use of supercritical carbon dioxide in this connection is particularly suitable [8]. 

Keurentjes et al. performed a continuous hydrogenation of 1-butene in supercritical carbon dioxide.[9,10] A fluorous derivative of Wilkinson s catalyst was prepared in situ by mixing the ligand with [(COD)RhCl]2 under hydrogen / carbon dioxide pressure (Figure 4.37). 

This chapter reviews recent findings about the health benefits of phytochemicals present in fruits, vegetables, nuts, seeds, and herbs, including phenolics, carotenoids, sterols, and alkaloids. These phytochemicals are extracted using emerging technologies such as supercritical carbon dioxide (SC-CO2) extraction, PEF, MWE, HPP, UE, and OH. The impact of important parameters related to sample preparation (particle size and moisture content) and extraction process (temperature, pressure, solvent flow rate, extraction time, and the use of a cosolvent) on the efficiency of extraction and on the characteristics of the extracted products is evaluated based on an extensive review of recent literature. The future of extraction of phytochemicals is certainly bright with the... 

J. P. DeYoung, J. Kalda, and J. M. DeSimone, Decomposition kinetics of perfluoroalkyl acyl peroxides in liquid and supercritical carbon dioxide, in preparation. 

SR042 Breu, W., M. Hagenlocher, K. Redl, G. Tittel, F. Stadler, and H. Wagner. Antiinflammatory activity of sabal fruit extracts prepared with supercritical carbon dioxide. In vitro antagonists of cyclooxygenase and 5-lipoxygenase metabolism. Arzneimittelforschung 1992 42(4) 547-551. 

Extraction of 25 different binary mixtures of racemic acids (2-(4-isobutylphenyl)-propionic acid (1), and cis- and trans-chrysanthemic (2)), and various chiral bases with supercritical carbon dioxide permitted the conclusion that molecular chiral differentiation in a supercritical fluid is more efficient than in conventional solvents. In the majority of cases, however, complete separation could not be achieved. In five cases, remarkable partial resolutions were realized (30-75% ee) and resolution was possible on a preparative scale. The pair ds-chrysanthemic acid and (S)-(-i-)-2-(benzylamino)-1-butanol (3) was studied in detail. Pressure, temperature, and time, as well as the molar ratio of base and acid, had a marked influence on the quantity and quality of the products. Increasing pressure or decreasing temperature resulted in higher ee values. (-)-cw-Chrysanthemic acid in 99% ee was obtained from the raffinate in a single extraction step. Multiple extractions produced the (-i-)-cA-acid in 90% ee (see fig. 6.3) (Simandi et al., 1997). 

The resinoids described above should be distinguished from prepared oleoresins (e.g., pepper, ginger, and vanilla oleoresins), which are concentrates prepared from spices by solvent extraction. The solvent that is used depends on the spice currently, these products are often obtained by extraction with supercritical carbon dioxide [223a]. Pepper and ginger oleoresins contain not only volatile aroma compounds, but also substances responsible for pungency. 

Shiho, H. DeSimone, J. M. Preparation of Micron-Size Polystyrene Particles in Supercritical Carbon Dioxide. J. Polym. Sci., Part A Polym. Chem. 1999, 37, 2429-2437. 

Preparation and Studies of Polymer/Polymer Composites Prepared Using Supercritical Carbon Dioxide... 

Kung, E. Lesser, A. J. McCarthy, T. J. Morphology and Mechanical Performance of Polystyrene/Polyethylene Composites Prepared in Supercritical Carbon Dioxide. Macromolecules 1998, 31, 4160. 

Fluoromethylbenzoic acids, metallation, 9, 26-27 Fluoro(phenyl) complexes, with platinum(II), 8, 482 Fluorosilanes, elimination in fluorinated alkene activation, 1, 732 in fluorinated aromatic activation, 1, 731 and hydrodefluorination, 1, 748 Fluorosilicate anions, hypercoordinated anions, 3, 484 Fluorotoluenes, metallation, 9, 21 Fluorous alkylstannanes, preparation, 3, 820 Fluorous biphasic system, as green solvent, 12, 844 Fluorous ligands, with supercritical carbon dioxide, 1, 82 Fluorous media... 

Kwon K-T, Uddin MS, Jung G-W et al (2011) Preparation of micro particles of functional pigments by gas-saturated solution process using supercritical carbon dioxide and polyethylene glycol. Korean J Chem Eng 28(10) 2044-2049... 

Computer Chips. The manufacture of computer chips requires excessive amounts of chemicals, water, and energy. Estimates indicate that the weight of chemicals and fossil fuels required to make a computer chip is 630 times the weight of the chip, as compared to the 2 1 ratio for the manufacture of an automobile. Scientists at the Los Alamos National Laboratory have developed a process that uses supercritical carbon dioxide in one of the steps in chip preparation, and it significantly reduces the quantities of chemicals, energy, and water needed to produce chips. 

Krocher, O., Koppel, R.A., Froba, M. and Baiker, A. (1998) Silica hybrid gel catalysts containing group(VIII) transition metal complexes preparation, structural, and catalytic properties in the synthesis of N, N-dimethylformamide and methyl formate from supercritical carbon dioxide. Journal of Catalysis, 178, 284-298. 

Koushik, K. and U.B. Kompella (2004) Preparation of large porous deslorelin-PLGA microparticles with reduced residual solvent and cellular uptake using a supercritical carbon dioxide process. Pharmaceutical Research, 21 p. 524-535. 

Other reagents and solvents were obtained from commercial sources. The samples were prepared by mixing various chiral bases with racemic acids in 0.5 1 molar ratio. A porous supporting material (Perfilt), impregnated with these mixtures, was put into the extractor vessel and extracted with supercritical carbon dioxide. 

A CLEA prepared from CaLB was recently shown to be an effective catalyst for the resolution of 1-phenylethanol and 1-tetralol in supercritical carbon dioxide in continuous operation [47]. Results were superior to those obtained with Nov 435 (CaLB immobilized on a macroporous acrylic resin) under the same... 

Even in its simplified form, the Nelson protocol will deter the most enthusiast natural-product chemist. Unsurprisingly, alternative protocols have been described in the proprietary literature, and their sheer number testify to the ingenuity and commitment of chemists to solve what is still today a daunting task. Some modern modifications to the Nelson method from the proprietary literature include the use of supercritical carbon dioxide to reduce the extraction of pigments in the preparation of the oleoresin [54], and the recourse to macroporous adsorption resins [55] or to repeated extraction with aqueous silver nitrate to trap capsaicinoids and reduce the number of partition steps [56]. 

---