Supercritical extraction description

A breakdown according to cost centres reveals that investment costs (interest and depreciation) are the major cost factor of production at about 40%, followed by personnel, energy, consumables, maintenance and administration expenses. A more detailed description including plant price indices, operating expenses and profitability as well as more details on supercritical extraction mechanisms and modelling of solid botanical matrices and a presentation of the Latin American scenario are given in a recent review article [11]. 

In a first step of the process propane, butane, pentane, or hexane is used to extract vanidyl porphyrins from residual oil. The liquid extract of hydrocarbon and porphyrins is next subjected to supercritical CO2 exU action between 90and 130 °Fand 1,075 to 8,000 psi. At almost all combinations of these pressures and temperatures the C3 through C(, paraffins are miscible in CO2. With a supercritical extraction column we wonder what ratio of C02-lo-extract would result in purified oil and what happens to the vanidyl porphyrins. In the process diagram and description, the supercritical C02-liquid solvent extract is expanded to an unspecified different pressure and temperature. But, it is important to relate that pentane and hexane are miscible with CO2 at room temperature and 800 psi so that the expansion would have to be to conditions higher in temperature and lower in pressure to separate CO2 and hexane. For propane the miscibility conditions extend to much lower pressure and so the separation of propane from carbon dioxide becomes problematic. 

The coupling of supercritical fluid extraction (SEE) with gas chromatography (SEE-GC) provides an excellent example of the application of multidimensional chromatography principles to a sample preparation method. In SEE, the analytical matrix is packed into an extraction vessel and a supercritical fluid, usually carbon dioxide, is passed through it. The analyte matrix may be viewed as the stationary phase, while the supercritical fluid can be viewed as the mobile phase. In order to obtain an effective extraction, the solubility of the analyte in the supercritical fluid mobile phase must be considered, along with its affinity to the matrix stationary phase. The effluent from the extraction is then collected and transferred to a gas chromatograph. In his comprehensive text, Taylor provides an excellent description of the principles and applications of SEE (44), while Pawliszyn presents a description of the supercritical fluid as the mobile phase in his development of a kinetic model for the extraction process (45). 

Description of extraction of grape seed oil by means of liquid and supercritical carbon dioxide as solvent (Gomez et al., 1996). 

Starting with a description of the analytical challenge in Chapter 19, the third part, which is devoted to analytical attitudes, proceeds with a detailed description in Chapter 20 of modern sample preparation procedures including solid-phase extraction, matrix solid-phase dispersion, use of restricted-access media, supercritical fluid extraction, and immunoaffinity cleanup. Flexible derivatization techniques including fluorescence, ultraviolet-visible, enzymatic, and photochemical derivatization procedures are presented in Chapter 21. 

The Model 50 Supercritical Fluid Microextractor from the Suprex Co. (Pittsburgh, PA) was adapted for this design. A schematic of our multi-vessel extractor design can be found in Figures 1 and 2, for six and twelve multi-vessel systems, respectively. The following is a detailed description of the main components. The design, explained here for the extraction from six and twelve vessels is in principle applicable to any number of vessels, provided that other components of the system are scaled up. 

The description of the design changes to a conventional supercritical fluid extraction unit are presented here in order of introduction to the flow pattern of the fluid. 

The techniques used were based on solvent extraction (e.g. with pentane), complexation (e.g. with diethyldithiocarbamate, EDTA), derivatisation (e.g. hydride generation, propylation or ethylation), and capillary GC separation followed by a range of detection techniques (e.g. QFAAS, ICPMS, MIP-AES, MS) DPASV has also been successfully used. In the frame of this project, two new techniques were also developed and successfully applied, namely supercritical fluid extraction followed by CGC/MS and isotope dilution ICPMS after ethylation and CGC separation. A full description of the techniques is given elsewhere (Quevauviller, 1998b). 

Numerous extraction methods and techniques have been developed and reported, especially if one takes into account the variety of modifications. The most common and simple general classification of these methods is similar to that introduced in chromatography and based on the kind of phase to which the analyte is transferred. One can distinguish the extractions as liquid, solid, gas, and supercritical fluid phase extractions. More precise description specifies the two phases between which the analyte is distributed (e.g., liquid-liquid or solid-liquid [leaching] extractions). The latter methods are all called solvent extraction. 

Traditional methods of extraction, such as Soxhlet, have been replaced by modern techniques as supercritical fluid extraction (SFE), microwave-assisted extraction (MAE), ultrasonic extraction, and accelerated solvent extraction (ASE) during recent years. The application of specific methods to these kinds of samples has permitted the development of a great number of other extraction methods. In the following list, a brief description is given ... 

A detailed description of the experimental apparatus and procedure used for the aqueous study are given elsewhere (Roop and Akgerman, Ind. Eng. Chem. R., in review) Static equilibrium extractions were carried out in a high pressure equilibrium cell (300 mL Autoclave). After the vessel is initially charged with 150 mL of water containing 6.8 wt.% phenol and supercritical carbon dioxide (and a small amount of entrainer, if desired), the contents were mixed for one hour followed by a two hour period for phase separation. Samples from both the aqueous phase and the supercritical phase were taken for analysis and the distribution coefficient for phenol calculated. 

The focus in Chapters 7 and 8 is on the specific sample preparation approaches available for the extraction of organic compounds from environmental matrices, principally soil and water. Chapter 7 is concerned with the role of Soxhlet, ultrasonic and shake-flask extraction on the removal of organic compounds from solid (soil) matrices. These techniques are contrasted with newer developments in sample preparation for organic compound extraction, namely supercritical fluid extraction, microwave-assisted extraction and pressurized fluid extraction. Chapter 8 is arranged in a similar manner. Initially, details are provided on the use of solvent extraction for organic compounds removal from aqueous samples. This is followed by descriptions of the newer approaches, namely solid-phase extraction and solid-phase microextraction. 

This is the first of the coffee decaffeination patents that describe a continuous, counter-current liquid-liquid extraction. A brief description of the process is provided here. A water extract of roasted coffee beans, called coffee liquor, which contains aromas and caffeine and other water soluble components such as carbohydrate and protein materials is fed to a vacuum suipper. The extract is concentrated to about 30-50% in an evaporator-condenser and is fed to a sieve tray tower. The liquor passes across the hays in the tower downward through downspouts countercurrent to supercritical CO2 which enters the tower at the bottom and passes upward through the holes in the sieve trays. CO2 extracts caffeine from the liquor, and the decaffeinated liquor leaves the near the bottom of tower. The condensate water from the vacuum stripper prior to the tray tower is fed to the sieve trays in the top section of the tower. The water washes the caffeine from the supercritical CO2 passing upward. The caffeine-free CO2 is recycled to the bottom of the column. 

The invention concerns the use of supercritical solvents to extract the cocoa butter from cocoa nibs (comminuted cocoa beans) and cocoa mass (fmely crushed beans). The description of other processes in the prior art section of the patent points out that organic solvent extraction results in the presence of residual solvents. Additionally, some of the newer pressing methods, via expellors, for example, introduce waste bean contaminants into the butter which must be removed with economic and taste penalties. 

Hydrogenation of the extracted impurities is described in the detailed description of the invention as a means of rendering the exUacted materials nontoxic, e.g., the hydrogenation of PCBs to nonloxic hydrocarbons. Increasingly, we find that many of the supercritical fluid patents that are issuing are not not obvious to those skilled in the art. ... 

The extraction of substances from solid substrates with supercritical solvents can be analyzed and modeled in a simple way by considering only the medium values and by determination of unknown coefficients by fitting to the extraction curve and a mass balance [1]. This approach results in simple equations that can represent parts of the extraction curve sufficiently, but fail for others, especially during the first part of the extraction. If the process is to be modeled more accurately, the analysis is far more complex and beyond the scope of this chapter. Nevertheless, some parameters determining the extraction and influencing the result are listed below together with the description of a simplified model that may provide some insight into the applied methods. 

CO2 is used widely as a solvent for extraction. The advantages of using supercritical CO2 include its low toxicity, low cost, nonflammability, and ease of disposal. Once the extraction is complete and the pressure returns to atmospheric pressure, the carbon dioxide immediately changes to a gas and escapes from the opened extraction vessel. The pure extracted analytes are left behind. Automated SFE instruments can extract multiple samples at once at temperatures up to 150°C and pressures up to 10,000 psi (psi means pounds per square inch and is not an SI unit 14.70 psi = 1 atm). SFE instrument descriptions and applications from one manufacturer, Isco, Inc., can be found at their website (www.isco.com). The SFE methods have been developed for extraction of analytes from environmental, agriculmral, food and beverage, polymer and pharmaceutical samples, among other matrices. 

Supercritical anti-solvent micronization can be performed using different processing methods and equipment [17]. Different acronyms were used by the various authors to indicate the micronization process. It has been referred to as GAS (gas anti-solvent), PCA (precipitation by compressed anti-solvent), ASES (aerosol solvent extraction system), SEDS (solution enhanced dispersion by supercritical fluids), and SAS (supercritical anti-solvent) process [8,17]. Since the resulting solid material can be signiflcantly influenced by the adopted process arrangement, a short description of the various methods is presented below. 

In the last decades, some more environment friendly procedures have been suggested for com germ oil production, among them, the use of enzymes to enhance the oil recovery and/or extraction of oil by using supercritical fluid extraction (SFE) (Matthaus, 2012). This chapter is focused on the SFE process of com germ oil, paying special attention to the description of the process and the influence of process parameters on the quality of the resulting oil. 

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