MICROWAVE ASSISTED EXTRACTION 

Microwave-Assisted Extraction (MAE) is a sample preparation technique that uses microwave energy to rapidly heat and extract analytes from a sample matrix. MAE is a more efficient and effective extraction technique than traditional methods, such as Soxhlet extraction, because it uses less solvent and time.

General Procedure 

The following is a general procedure for microwave-assisted extraction:Prepare the sample. Grind or homogenize the sample to a fine powder.

1. Weigh the sample and solvent. A typical ratio of sample to solvent is 1:10.
2. Place the sample and solvent in a microwave vessel. The vessel should be sealed to prevent solvent evaporation.
3. Place the vessel in the microwave oven. Set the microwave power to 50-70% and the temperature to 100-120°C.
4. Heat the sample for 5-10 minutes. The exact extraction time will depend on the sample matrix and analytes of interest.
5. Allow the sample to cool.
6. Filter the sample to remove the solid matrix.
7. Collect the filtrate for analysis.

Advantages 

1. Efficiency: MAE can extract multiple samples simultaneously using minimal organic solvent.
2. Time-saving: It significantly reduces the extraction time.
3. Improved Yield: It often results in an improved yield of the extracted compounds.
4. Better Accuracy: It provides better accuracy in the extraction process.
5. Suitable for Thermolabile Substances: It is suitable for extracting thermolabile substances.
6. Cost-effective: It leads to better products at a lower cost.

Disadvantages 

• High cost of equipment. MAE requires specialized equipment, such as a microwave oven and microwave-safe vessels. This can be a significant cost barrier for some laboratories.
• Limited selectivity. MAE is not very selective, meaning that it can extract a wide range of compounds from a sample matrix. This can be both a good and a bad thing. On the one hand, it allows for the extraction of a wide range of compounds of interest. On the other hand, it can also lead to the extraction of unwanted compounds that can interfere with the analysis.
• Safety concerns. MAE can be dangerous if not used properly. The microwave energy can cause the solvent to boil and create pressure, which could lead to an explosion. It is important to use proper safety precautions when working with MAE, such as using a microwave oven with a pressure relief valve.

Applications 

1. Extraction of Terpenes: Closed vessel techniques of MAE are used for the extraction of terpenes.
2. Fungicides: Extraction of fungicides like hexaconzole via MAE from weathered soil can also be done.
3. Polymer Research: Extraction of additives polypropylene and polyethylene in the field of polymer research.
4. Plant Protein Extraction: MAE has been successfully used for plant protein extraction.
5. Oil Extraction: It’s used for extracting oil from tar sands.
6. Waste Management: Extraction of chitin from seafood waste.
7. Biofuel Production: MAE is used in the production of biofuels
8. Food analysis: MAE can be used to extract pesticides, herbicides, and other contaminants from food samples. For example, MAE has been used to extract aflatoxins from peanuts, mycotoxins from maize, and heavy metals from rice.
9. Environmental analysis: MAE can be used to extract heavy metals, organic pollutants, and other contaminants from environmental samples, such as soil, water, and sediment. For example, MAE has been used to extract polycyclic aromatic hydrocarbons (PAHs) from soil, heavy metals from water, and persistent organic pollutants (POPs) from sediment.
10. Clinical analysis: MAE can be used to extract drugs, metabolites, and other biomarkers from clinical samples, such as blood, urine, and tissue. For example, MAE has been used to extract anticancer drugs from plasma, steroids from urine, and DNA from tissue samples.