Extraction Technologies for Medicinal and Aromatic ... - Capacity4Dev

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1 AN OVERVIEW OF EXTRACTION TECHNIQUES FOR MEDICINAL AND AROMATIC PLANTS fl ow and pressure control, and restrictors. Generally, cylindrical extraction vessels are used for SFE and their performance is good beyond any doubt. The collection of the extracted analyte following SFE is another important step: signifi cant analyte loss can occur during this step, leading the analyst to believe that the actual effi ciency was poor. There are many advantages to the use of CO 2 as the extracting fl uid. In addition to its favorable physical properties, carbon dioxide is inexpensive, safe and abundant. But while carbon dioxide is the preferred fl uid for SFE, it possesses several polarity limitations. Solvent polarity is important when extracting polar solutes and when strong analyte-matrix interactions are present. Organic solvents are frequently added to the carbon dioxide extracting fl uid to alleviate the polarity limitations. Of late, instead of carbon dioxide, argon is being used because it is inexpensive and more inert. The component recovery rates generally increase with increasing pressure or temperature: the highest recovery rates in case of argon are obtained at 500 atm and 150° C. The extraction procedure possesses distinct advantages: i) The extraction of constituents at low temperature, which strictly avoids damage from heat and some organic solvents. ii) No solvent residues. iii) Environmentally friendly extraction procedure. The largest area of growth in the development of SFE has been the rapid expansion of its applications. SFE fi nds extensive application in the extraction of pesticides, environmental samples, foods and fragrances, essential oils, polymers and natural products. The major deterrent in the commercial application of the extraction process is its prohibitive capital investment. 1.2.1.11 Phytonics Process A new solvent based on hydrofl uorocarbon-134a and a new technology to optimize its remarkable properties in the extraction of plant materials offer signifi cant environmental advantages and health and safety benefi ts over traditional processes for the production of high quality natural fragrant oils, fl avors and biological extracts. Advanced Phytonics Limited (Manchester, UK) has developed this patented technology termed “phytonics process”. The products mostly extracted by this process are fragrant components of essential oils and biological or phytopharmacological extracts which can be used directly without further physical or chemical treatment. 26
EXTRACTION TECHNOLOGIES FOR MEDICINAL AND AROMATIC PLANTS The properties of the new generation of fl uorocarbon solvents have been applied to the extraction of plant materials. The core of the solvent is 1,1,2,2-tetrafl uoroethane, better known as hydrofl uorocarbon-134a (HFC-134a). This product was developed as a replacement for chlorofl uorocarbons. The boiling point of this solvent is -25° C. It is not fl ammable or toxic. Unlike chlorofl uorocarbons, it does not deplete the ozone layer. It has a vapor pressure of 5.6 bar at ambient temperature. By most standards this is a poor solvent. For example, it does not mix with mineral oils or triglycerides and it does not dissolve plant wastes. The process is advantageous in that the solvents can be customized: by using modifi ed solvents with HFC-134a, the process can be made highly selective in extracting a specifi c class of phytoconstituents. Similarly, other modifi ed solvents can be used to extract a broader spectrum of components. The biological products made by this process have extremely low residual solvent. The residuals are invariably less than 20 parts per billion and are frequently below levels of detection. These solvents are neither acidic nor alkaline and, therefore, have only minimal potential reaction effects on the botanical materials. The processing plant is totally sealed so that the solvents are continually recycled and fully recovered at the end of each production cycle. The only utility needed to operate these systems is electricity and, even then, they do no consume much energy. There is no scope for the escape of the solvents. Even if some solvents do escape, they contain no chlorine and therefore pose no threat to the ozone layer. The waste biomass from these plants is dry and “ecofriendly” to handle. 1.2.1.11.1 Advantages of the Process • Unlike other processes that employ high temperatures, the phytonics process is cool and gentle and its products are never damaged by exposure to temperatures in excess of ambient. • No vacuum stripping is needed which, in other processes, leads to the loss of precious volatiles. • The process is carried out entirely at neutral pH and, in the absence of oxygen, the products never suffer acid hydrolysis damage or oxidation. • The technique is highly selective, offering a choice of operating conditions and hence a choice of end products. • It is less threatening to the environment. • It requires a minimum amount of electrical energy. • It releases no harmful emissions into the atmosphere and the resultant waste products (spent biomass) are innocuous and pose no effl uent disposal problems. • The solvents used in the technique are not fl ammable, toxic or ozone depleting. • The solvents are completely recycled within the system. 27
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7 DISTILLATION TECHNOLOGY FOR ESSEN
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9 SOLID PHASE MICRO-EXTRACTION AND
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12 FLASH CHROMATOGRAPHY AND LOW PRE
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13 COUNTER-CURRENT CHROMATOGRAPHY 1
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