SFE continues to find applications too numerous to mention in this update. Specialty products such as polyunsaturated fatty acid esters derived from fish oils, neat and roasted sesame oil, cranberry seed-based oils, oils high in n and n-6 fatty acid content, pumpkin seed and sea-buckthorn seed-derived extracts, mustard seed oil, SC-CO 2 -derived chia seed oil, and fiber for nutraceutical use join the traditional SFE-derived products, including decaffeinated coffee, hops extract, ginseng, and spice and antioxidant extracts.
The lipophilic extract, using predominantly SC-CO 2 , from sawtooth palmetto berry is a proven treatment for prostate problems. Newer niche products have emerged in the past two years such as ayurvedic medicine extractives that are produced by extraction with SC-CO 2 followed by a hydro-ethanolic pressurized solvent extraction.
Hyphenated Techniques in Supercritical Fluid Chromatography and Extraction, Volume 53
An array of critical fluid-based processing operations can be applied to a common agricultural commodity such as rice or rice bran. Hence, SFE can be applied to derive the oil, which can then be fractionated using SC-CO 2 or hydrolyzed into its constituent fatty acids by using subcritical water. In the late s, the cosmetic industry paid little attention to lipophilic extractives derived by SC-CO 2 extraction. These new marketplace developments are important since current schemes for processing algae-derived oils for biodiesel use advocate the removal of higher-value lipophilic components such as antioxidants and pigments prior to conversion to methyl esters for use as biodiesel.
For information, visit issf He has over 40 years of experience in supercritical fluid technology and separation science, is the author of publications, holds three patents, and has received numerous scientific awards. King, J. List eds. Eggers, R. King and G.
ACS Symposium Series (ACS Publications)
List, eds. Temelli, F.
Fluids 47 — Brunner, G. Brown, E. Grushka, and S. Lunte eds.
McDonald and M. Mossoba eds. Habulin, Compressed gases as alternative enzymatic-reaction solvents: a short review, J. Fluids 23 —42 List, G. King eds. Oil Chem. Working for Air Products. SFE can be used to prepare analytical samples from complex solid samples by extracting the desired compounds, for example extracting components from soils or sediments.
The technique uses liquid Carbon Dioxide in most cases which is heated and pressurised to certain levels to become supercritical, in other words having properties of both a gas and a liquid. In its supercritical state, CO 2 acts as a solvent and can dissolve or extract materials within a sample. Our range includes high quality cylinder regulators, manifolds, valves and purge systems which will help to optimise the smooth operation and accuracy of your analysis. If you require any additional advice on the right purity grade for your needs, please contact us.
Increasing pressure affects supercritical fluid molecules to become closer to each other and decreases diffusivity in the material. The greater diffusivity gives supercritical fluids the chance to be faster carriers for analytical applications. Hence, supercritical fluids play an important role for chromatography and extraction methods. Thus, supercritical fluids are less resistant than liquids towards components flowing through. The viscosity of supercritical fluids is also distinguished from that of liquids in that temperature has a little effect on liquid viscosity, where it can dramatically influence supercritical fluid viscosity.
These properties of viscosity, diffusivity, and density are related to each other. The change in temperature and pressure can affect all of them in different combinations. For instance, increasing pressure causes a rise for viscosity and rising viscosity results in declining diffusivity. Generally, HPLC has better selectivity that SFC owing to changeable mobile phases especially during a particular experimental run and a wide range of stationary phases. SFC enables change of some properties during the chromatographic process. This tuning ability allows the optimization of the analysis.
They use similar stationary phases with similar column types. However, there are some differences. Temperature is critical for supercritical fluids, so there should be a heat control tool in the system similar to that of GC. Also, there should be a pressure control mechanism, a restrictor, because pressure is another essential parameter in order for supercritical fluid materials to be kept at the required level.
A microprocessor mechanism is placed in the instrument for SFC. This unit collects data for pressure, oven temperature, and detector performance to control the related pieces of the instrument. Adapted from D. Skoog and J. Open-tubular columns and packed columns are the two most common types used in SFC. Open-tubular ones are preferred and they have similarities to HPLC fused-silica columns.
This type of column contains an internal coating of a cross-linked siloxane material as a stationary phase. The thickness of the coating can be 0. The length of the column can range from of 10 to 20 m. There is a wide variety of materials used as mobile phase in SFC. The mobile phase can be selected from the solvent groups of inorganic solvents, hydrocarbons, alcohols, ethers, halides; or can be acetone, acetonitrile, pyridine, etc.
The most common supercritical fluid which is used in SFC is carbon dioxide because its critical temperature and pressure are easy to reach. Additionally, carbon dioxide is low-cost, easy to obtain, inert towards UV, non-poisonous and a good solvent for non-polar molecules.
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Other than carbon dioxide, ethane, n-butane, N 2 O, dichlorodifluoromethane, diethyl ether, ammonia, tetrahydrofuran can be used. Some other detectors which are used with HPLC can be attached to SFC such as fluorescence emission spectrometer or thermionic detectors. Lower viscosity leads to high flow speed for the mobile phase.
Thanks to the critical pressure of supercritical fluids, some fragile materials that are sensitive to high temperature can be analyzed through SFC. High pressure conditions provide a chance to work with lower temperature than normally needed. Hence, the temperature-sensitive components can be analyzed via SFC. In addition, the diffusion of the components flowing through a supercritical fluid is higher than observed in HPLC due to the higher diffusivity of supercritical fluids over traditional liquids mobile phases.
This results in better distribution into the mobile phase and better separation. The applications of SFC range from food to environmental to pharmaceutical industries. In this manner, pesticides, herbicides, polymers, explosives and fossil fuels are all classes of compounds that can be analyzed.
SFC can be used to analyze a wide variety of drug compounds such as antibiotics, prostaglandins, steroids, taxol, vitamins, barbiturates, non-steroidal anti-inflammatory agents, etc.
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Chiral separations can be performed for many pharmaceutical compounds. SFC is dominantly used for non-polar compounds because of the low efficiency of carbon dioxide, which is the most common supercritical fluid mobile phase, for dissolving polar solutes. SFC is used in the petroleum industry for the determination of total aromatic content analysis as well as other hydrocarbon separations.
The unique physical properties of supercritical fluids, having values for density, diffusivity and viscosity values between liquids and gases, enables supercritical fluid extraction to be used for the extraction processes which cannot be done by liquids due to their high density and low diffusivity and by gases due to their inadequate density in order to extract and carry the components out. Complicated mixtures containing many components should be subject to an extraction process before they are separated via chromatography. An ideal extraction procedure should be fast, simple, and inexpensive.
In addition, sample loss or decomposition should not be experienced at the end of the extraction. Following extraction, there should be a quantitative collection of each component.