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Microwave Assisted Extraction


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My pharmacognosy presentation on Microwave Assisted Extraction

Published in: Health & Medicine
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Microwave Assisted Extraction

  1. 1. Microwave-assisted Extraction (MAE) Presented by: Naraino Majie Nabiilah Date: 28th August 2014
  2. 2. Table of Content • Introduction • Microwave theory • Extraction principle • Instruments – Closed vessel – Open vessel • Application of MAE • Factors affecting MAE • Conclusion
  3. 3. INTRODUCTION • Microwave-assisted extraction is an efficient method which involves deriving natural compounds from raw plants. • Microwave extraction allows organic compounds to be extracted more rapidly, with similar or better yield as compared to conventional extraction methods.
  4. 4. INTRODUCTION • MAE of anthraquinone in pure alcohol at 60°C for 30mins gave a recovery of 65% which resulted from 3 days maceration in pure ethanol at room temperature. • The advantages that MAE has over Soxhlet are: – Reduction in extraction time – Improved yield – Better accuracy – Suitable for thermolabile substances
  6. 6. MICROWAVE THEORY • Microwaves are non-ionizing electromagnetic waves of frequency between 300MHz to 300 GHz and positioned between the X-ray and infrared rays in the electromagnetic spectrum. • Microwaves serves two major purposes: – Communication – Energy vectors
  7. 7. MICROWAVE THEORY • The energy vector application is the direct action of waves on materials that has the ability to convert a part of the absorbed electromagnetic energy to heat energy. • Microwaves are made up of two oscillating perpendicular field’s i.e. – Electric field – Magnetic field
  8. 8. MICROWAVE THEORY • In MAE, heating occurs in a targeted and selective manner with practically no heat being lost to the environment as the heating occurs in a closed system. • This unique heating mechanism significantly reduces the extraction time (usually less than 30min) as compared to Soxhlet.
  9. 9. EXTRACTION PRINCIPLE • Dried plants contain a minute microscopic trace of moisture which serves as target for microwave heating. • High temperature and pressure is generated inside the oven. • High temperature causes dehydration of cellulose which accounts for its reduction of mechanical strength.
  10. 10. EXTRACTION PRINCIPLE • The MAE process is as follows: – Microwave radiation – Moisture get heated up – Moisture evaporates – Generation of tremendous pressure on cell wall – Swelling of plant cell – Rupture of the cell – Leaching out of phyto-constituents • This phenomenon can be intensified if the plant matrix is impregnated with solvents with higher heating efficiency under microwave.
  11. 11. INSTRUMENTS • There are two types of commercially available MAE systems: – Closed extraction vessels – Focused microwave ovens • The former performs extraction under controlled pressure and temperature. • In the latter, only a part of the extraction vessel containing the sample is irradiated with microwave.
  12. 12. Open and Closed-vessel system
  13. 13. INSTRUMENTS • Both systems are available as multi-mode and single-mode. • A multi-mode system allows evenly radiation of sample by random dispersion of microwaves. • Single-mode (aka focused system) allows focused radiation on a restricted zone by a much stronger electric field.
  14. 14. INSTRUMENTS • Both multi-mode and focused system comprises of the following four components: – Microwave generator: magnetron which generates microwave energy – Wave guide: propagate microwave to microwave cavity – The applicator: where the sample is placed – Circulator : allow microwave to move in forward direction
  15. 15. CLOSED VESSEL • With closed vessel extraction, pressurised microwave assisted extraction is performed under pressure (with or without regulation). • The pressure allows temperatures above boiling points of the solvents to be reached enhancing speed and efficiency. • To avoid overpressure, power, temperature and pressure can be controlled. • When dealing with thermolabile compounds, high temperature causes degradation of analytes. Therefore, the open system is chosen.
  16. 16. Advantages of closed-vessel system • Decreased in extraction time • Loss of volatile substances is avoided • Less solvent is required because no evaporation occurs • No hazardous fumes during acid microwave since it is a closed vessel
  17. 17. Disadvantages of closed-vessel system • High pressure used pose safety risks • The usual constituent material of the vessel does not allow high solution temperatures • Addition of reagents is impossible since it is a single step procedure • Vessel must be cooled down before it can be opened to prevent loss of volatile constituents.
  18. 18. OPEN VESSEL • Extraction is made at atmospheric pressure. • The maximum possible temperature is determined by the boiling point of the solvent at that pressure. • Losses of vapours are prevented by the presence of a cooling system on the top of the extraction vessel that causes condensation of solvent vapours. • Heating is homogenous and efficient.
  19. 19. Advantages of open-vessel system • Increased safety • Addition of reagent is possible • Vessels made of various material can be used • Excess solvent can be removed easily • Ability to process large samples • No requirement for cooling down or depressurisation • Low cost of equipment • Suitable for thermolabile products
  20. 20. Disadvantages of open-vessel system • The ensuing method are less precise than in close-vessel system • The sample throughput is lower as open system cannot process many samples simultaneously • Require longer time to achieve same results as for closed system
  23. 23. FACTORS AFFECTING MAE • Solvent - appropriate solvent is very important for obtaining optimal extraction yields.
  24. 24. FACTORS AFFECTING MAE • Extraction time - by increasing extraction time, quantity of analytes is increased but there is the risk of degradation.
  25. 25. FACTORS AFFECTING MAE • Microwave power - the power must be correctly chosen to minimise the time needed for extraction. • However, increased power may cause solvent loss by evaporation. • Maximum power used ranges between 600W and 1000W for closed systems and around 250Wfor open systems.
  26. 26. FACTORS AFFECTING MAE • Matrix characteristics - the plant particle size and the status in which it is presented for MAE can affect the recoveries of compounds. • The particle sizes of the extracted materials are generally in the range of 100m – 2mm. • Fine powders enhance extraction as they provide a larger surface area.
  27. 27. FACTORS AFFECTING MAE • Temperature - temperature should be sufficient to ensure good solubility of compounds and a good penetration of solvent in the plant matrix to enhance extraction yield. • However, it should not be too high enough to degrade the target compounds.
  28. 28. CONCLUSION • Chemical analysis of extracts from plant material plays a central role in development and modernization of herbal medicine. • MAE has proven to be effective in all aspects compared to traditional extraction techniques. • More research is needed to improve the design and scale up of the novel extraction systems for their better industrial applications.
  29. 29. REFERENCES • S. Hemalatha, 2007, Microwave Assisted Extraction – An innovative and promising Extraction Tool for Medical, Pharmacognosy Reviews, Vol 1-Issue 1 • Farid Chemat, Giancarlo Cravotto, 2012, Microwave-assisted Extraction for Bioactive Compounds: Theory and Practice, Ebook • Mauricio A. Rostagno, Juliana M. Prado, 2013, Natural Product Extraction: Principles and Applications, Ebook • YouTube videos: – o – YE
  30. 30. THANK YOU