Microwave-assisted extraction disadvantages

Ultrasound-assisted leaching has also been used to extract natural compounds such as vitamins A, D and E from feeds [57], paclitaxel and related taxoids from leaf tissue of Taxus [58], opiates from hair samples [59] and antioxidants from rosemary [60]. Ultrasounds have so far had much more restricted application in this field than in the previous ones, possibly as a result of the technique being at a disadvantage with respect to alternatives such as microwave-assisted extraction [57] or supercritical CO, extraction [60]. 

Other extraction methods like (Ultra-Turrax) blending, ultrasonic, and solvent extractions are available. Most of these techniques show good recoveries for specific matrices, and after optimization of the extraction conditions. Microwave assisted extraction is another promising technique. Good recoveries for PCBs have been obtained. The extraction time is short, and samples can be extracted simultaneously. An overview of advantages and disadvantages of the various extraction techniques is given in Table 2. 

This chapter discusses the principal aspects of the technique in its two modes, the devices typically employed by each and their amenability to coupling with subsequent operations of the analytical process. Also, the main analytical applications of both modes in analytical chemistry are described, and their advantages and disadvantages with respect to alternative techniques such as Soxhlet, ultrasound-assisted, microwave-assisted or supercritical fluid extraction, discussed. 

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