Supercritical Fluid extraction

Introduction, concept,advantages, systems, Parts, working, solvents, modifiers, applications and its advancements

1. SUPERCRITICAL FLUID EXTRACTION Presented by – Jasmine Kaur M.Pharm (1 st ) year

2. INTRODUCTION Supercritical Fluid Extraction (SFE) is a eco-friendly alternative of extraction replacing organic solvents. In SFE use of Supercritical fluids (SCF’s) like supercritical CO2 as solvent is there. SCF are increasingly replacing organic solvents because of regulatory and environmental pressures on hydrocarbon and ozone depleting emissions. SCF helps in extraction of natural products of wide range of polarities.

3. CONCEPT Cagniard de la Tour discovered critical point (CP) in 1822. CP of pure substances is defined as the highest temperature and pressure at which the substances can exist in vapour - liquid equilibrium. At temperature and pressure above this point, a single homogenous fluid is formed, which is known as SCF. SCF is heavy like liquid but has penetration power like gas. SCF’s are produced by heating a gas above its critical temperature or compressing a liquid above its critical pressure but in this molar volume remains same irrespective of original form( liquid or gas). PHASE DAIGRAM

4. SFE can be used to extract active ingredients or analytes from various plants and microbial samples and useful in extraction of unknown natural products. Manipulating temperature and pressure of the fluid can solubilize the material of interest and selectively extract it.

5. ADVANTAGES Inexpensive Contaminant free Selectively Controllable Less costly to dispose safely than organic solvents. Oxidative and thermal degradation of active compounds is much less likely in SFE than in conventional solvent extraction and steam distillation methods.

6. SUPERCRITICAL FLUID EXTRACTION SYSTEMS SFE systems can be simple or complex based upon its design Analytical system- By this samples are prepared for chromatographic analysis and for the preparation of extracts in milligrams or grams. Preparative system- They are used for preparation of extracts. At pilot scale extracts are prepared in grams and at industrial scale extracts are prepared in kilograms. They are different configurations available based upon solids or liquids. SFE systems are available in various sizes in integrated and automated form. Manufactured by many commercial suppliers Eg :- Agilent Technologies, Perkin-Elmer, Supelco , CDS Analytical, Waters. Pilot scale system of SFE

7. Industrial scale system of SFE

8. PARTS OF SFE 1.Solvent pump 2. Modifier pump 3. Solid sample extraction cell 4. Fractionation Cell 5. Fractionation Cell 6. Valve SFE Pilot Plant equipped with two fractionation Cells Trapping vessel or analyte collection device

9. PARTS OF SFE SOLVENT PUMP - Solvent pump or CO2 pump delivers the fluid throughout the system. MODIFIER PUMP - It is necessary for increasing the polarity of solvent or supercritical CO2. Eg - Common modifier used is methanol in concentration of 1-10% EXTRACTION CELL OR COLUMN- It is made up of stainless steel to withstand high pressure with compression and fitting. Generally size of extraction cell ranges from 50-100 mL .The extraction cell is usually in an oven to control the temperature because any fluctuation in the temperature results in the change in SFE density and solvating property. FRACTINATION CELLS - Also know as separators, they can be one or more separators in which extracts are collected and the solvent is depressurized. VALVES- Helps in controlling process pressure, pumps flow rate, the chiller, the boiler and temperature in every section .

10. PARTS OF SFE Refrigerated system – It is along with the trapping vessel designed to trap the most volatile compounds. Recycling system - Recycle the SCF which have been employed. Extraction cell or column and the separators are commonly equipped with independent control of temperature and pressure. Because of this fractionation of the extracted compounds can be carried out by a stepwise depressurization. That’s, why we get different compounds within each separator, which are separated depending upon their differential solubility in SCF.

11. WORKING The sample is placed in an extraction vessel and pressurized with SCF CO2 to dissolve the sample. After extraction the extract is transferred to the fraction chamber and depressurized due to which CO2 loses its solvating power causing entire material to precipitate. Now the CO2 gets recycled . Precipitated material is extracted with addition of small amount of solvents.

12. SOLVENTS Supercritical CO2 is most widely used solvent because of its :- 1. Low critical parameters (31.1º C, 73.8 bar) 2. Low cost 3. Non- toxic Their has to use of SCF- grade CO2 because it is free from water, hydrocarbons and halocarbons. ( As cryogenic CO2 grade is not pure) Apart from CO2 other super critical fluids can be used given in Table.

13. SFE also uses some organic solvents, but these organic solvents are explosion-proof. Chlorofluorocarbons (CFCs) are good solvents because of their high density but their use has been restricted because of their effect on the ozone sphere. Now a days, water as SCF has become quite popular because of unique properties of water above its critical point. (374º C, 218 atm ) Above its critical point water becomes an excellent solvent for organic compounds and poor solvent for inorganic salts. This feature of water helps in extracting inorganic and organic compounds sequentially.

14. MODIFIERS Supercritical CO2 because of its low polarity is less effective in extracting more polar compounds from natural matrices. To overcome this problem, modifiers ( also called co-solvents) are commonly used. Modifiers- These are highly polar compounds that are added in small amounts can produce substantial changes in the solvent properties. A common modifier is methanol, typically 1-10%, which increases the polarity of supercritical C02.

15. PRESSURE SYSTEM The pump in the SFE, which is used to pressurize CO2 for achieving supercritical state, must be capable of generating high pressure and delivering reproducible volumes at a constant flow rate. Ideally, pumps deliver fluid at 0.5-4 mL/ min . SAMPLE PREPARATION Sample matrix in extraction vessels can be of various origins eg - plants, microbes and so on, and of several physical forms. For bulk matrix, it is essential to carry out some preliminary sample preparation which include grinding, sieving , drying, mixing, pH adjustment, or wetting, depending upon the physical form of the matrix. For non- porous or semiporous material, a smaller particle size allows more efficient and faster extraction .

16. In case of semi-solids, gel or liquid matrix it is necessary to immobilize the matrix on the solid support because SFE is generally not suitable for liquid samples. In that case matrix is applied to a piece of filter paper, a solid support such as diatomaceous earth or to a drying agent to carry out the extraction efficiently. For wet matrices water removal is essential to enhance the recovery and reproducibility of the extraction process .

17. EXTRACTION Static, dynamic, or recirculation modes can be used to perform SFE. In the static mode, the extraction cell is pressurized with SCF, and allowed to equilibrate prior to removal of the analyte for collection . In the dynamic mode, which appears to be the most popular among the three, SCF is passed through the extraction cell, and the analyte is collected continuously. In the recirculation mode, the same fluid is pumped through the sample for a while before it is repeatedly pumped to the collection device. Addition of a modifier can bring about enhanced efficiency of the SFE process. Modifier addition can be accomplished in three ways: By adding it (usually 500mL or less) directly to the sample in the extraction cell or by mixing it with the sample prior to loading in the extraction cell. By using CO2 gas cylinders containing premixed amounts of added modifier. By adding it in a continuous fashion with an external modifier pump which is most common method.

18. SAMPLE COLLECTION During sample collection C02 gas or any other solvent is depressurized due to which it converts to gaseous form and our extracted sample (analyte) is deposited in collection vial. The analyte is then washed with a small volume (usually 1-2 mL) of n-hexane, chloroform, iso -octane, ether or some other organic solvent.

19. APPLICATIONS SFE has long been used in industries for the extraction of various commercial natural products given in Table. In case of natural product extraction, extraction via SCF is predominantly limited to plant natural products and just handful of studies are carried out for extraction of microbial natural products via SFE . Sources from where the main bioactivities are extracted by SFE are antioxidant (41%), antitumor (18%) and antibacterial activity (10%), followed by antiviral, antimicrobial, anti-inflammatory and anticholinesterase ( upto 5%)

20. Extraction of essential oils :- essential oil extracted from black pepper, Jojoba oil from seeds of S immondia c hinesis . Extraction of Capsaicinoids from chilli pepper gives higher yield almost 96% of capsaicinoids and 80% of colour components has been fractionated by SFE. Flavanoids extraction- Quercetin from Onion skins, Epicatechin from sea coat of sweet Thai tamarind, ginkgolides from ginkgo leaves ( Ginkgo biloba ). Hyperforin highest content 35% was obtained from St. John Wort ( Hypericum perforatum ). Pathenolide about 80% is obtained from feverfew plants ( Tanacetum parthenium ). Taxol from Pacific yew tree ( Taxus brevifolia ) has been extracted by SFE. Astaxanthin from red yeast ( Phaffia Rhodozyma ) about 90% extraction yield can be obtained by SFE.

21. Rapid analysis for fat content : SFE have been used to determine the fat content of numerous products ranging from beef to oil seeds and vegetables. For the analysis of fats content in soybeans, sunflower, safflower, cottonseed, rapeseed and ground beef, it was found that supercritical fluid extraction yielded higher recoveries than those obtained by the AOCS approved methods. Rapid analysis for pesticides in foods :Supercritical fluid extraction provides an alternative to using organic solvents for the extraction of pesticides from their sample matrix. Some of the advantages which supercritical fluid extraction provides over the traditional methods of pesticide extraction are that the extraction can be performed in less time, and utilizes less solvent volume.

22. Advancements in SFE Combination of enzyme-assisted extraction (EAE) with SFE is pretreatment of biomass by use of enzymatic mixtures to promote cell wall hydrolysis deconstruction leading to an increased accessibility of the supercritical solvent to the matrix solute, thus increasing the extraction yield and selectivity. High intensity ultrasound as a technological improvement combined with SFE, comprises the control of frequency and power level which will lead to the formation and control of cavitation bubbles and repeated cycles of expansion and compression in the medium. These ultrasound cycles may lead to the rupture of cell walls of a biomass matrix substrate, favoring the penetration of the solvent and mass transfer. Thus, ultrasound has been used to provide higher yields and reduce extraction times. The design of experiments (DOE) or experimental design approach can provide a systematic investigation route as well as sequential steps for understanding linear and more complex types of interaction. The main goal of experimental design on SFE is to optimize the response variables of a certain sample by systematic modification of the controlling variables (e.g. temperature, pressure and time).

23. Nanoparticle formation using supercritical fluids: SFE were used in a number of different circumstances for the preparation of micro- nanodispersed organic systems. Supercritical drying: Supercritical drying goes beyond the critical point of the working fluid in order to avoid the direct liquid-gas transition seen in ordinary drying.

24. REFERENCES Satyajit D. Sarker , Zahid Latif, Alexander I. Gray. Natural products isolation. – Human Press. 2nd ed (2006) Pg no.-47-76 Rui P.F.F. da Silva, Teresa A.P. Rocha-Santos, Armando C. Duarte, Supercritical fluid extraction of bioactive compounds, Trends in Analytical Chemistry (2015), http://dx.doi.org/doi: 10.1016/j.trac.2015.11.013. M. Herrero, M. Castro- Puyana , J.A. Mendiola , E. Ibañez , Compressed fluids for the extraction of bioactive compounds, Trends Anal. Chem. 43 (2013) 67–83. J.L. Pasquel Reátegui , A.P.D.F. Machado, G.F. Barbero , C.A. Rezende , J. Martínez , Extraction of antioxidant compounds from blackberry ( Rubus sp.) bagasse using supercritical CO2 assisted by ultrasound, J. Supercrit . Fluids. 94 (2014) 223–33 . K.M. Sharif, M.M. Rahman, J. Azmir , A. Mohamed, M.H. a Jahurul , F. Sahena , I.S.M. Zaidul , Experimental design of supercritical fluid extraction - A review, J. Food Eng. 124 (2014) 105–16. Abbas K.A ., A . Mohamed, A.S . Abdulamir , H.A . Abas. Supercritical Fluid Extraction as New Analytical Method, American Journal of Biochemistry and Biotechnology 4 ( 2008) 345-53.

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