Microwave Assisted Extraction
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This document discusses microwave-assisted extraction (MAE), an efficient method for deriving natural compounds from plants. MAE uses microwave energy to heat plant materials mixed with solvents, extracting compounds faster than conventional methods. It describes the principles of microwave heating, closed and open vessel extraction systems, factors affecting MAE like solvent, time, power and temperature, and its applications. MAE provides benefits of reduced extraction time, improved yields, and ability to extract thermolabile substances.
Microwave Assisted Extraction
- 1. Microwave-assisted Extraction (MAE) Presented by: Naraino Majie Nabiilah Date: 28th August 2014
- 2. Table of Content • Introduction • Microwave theory • Extraction principle • Instruments – Closed vessel – Open vessel • Application of MAE • Factors affecting MAE • Conclusion
- 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. 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
- 5. INTRODUCTION
- 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. 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. 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. 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. 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. 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. Open and Closed-vessel system
- 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. 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. 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.
- 17. 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
- 18. 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.
- 19. 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.
- 21. 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
- 22. 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
- 25. FACTORS AFFECTING MAE • Solvent - appropriate solvent is very important for obtaining optimal extraction yields.
- 26. FACTORS AFFECTING MAE • Extraction time - by increasing extraction time, quantity of analytes is increased but there is the risk of degradation.
- 27. 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.
- 28. 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 100m – 2mm. • Fine powders enhance extraction as they provide a larger surface area.
- 29. 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.
- 30. 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.
- 31. 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: – https://www.youtube.com/watch?v=oFSe4HaPgg o – https://www.youtube.com/watch?v=3Em9qU4_2 YE
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