Microwave-Assisted Extraction - Advantages

Theoretical and applied aspects of microwave heating, as well as the advantages of its application are discussed for the individual analytical processes and also for the sample preparation procedures. Special attention is paid to the various preconcentration techniques, in part, sorption and extraction. Improvement of microwave-assisted solution preconcentration is shown on the example of separation of noble metals from matrix components by complexing sorbents. Advantages of microwave-assisted extraction and principles of choice of appropriate solvent are considered for the extraction of organic contaminants from solutions and solid samples by alcohols and room-temperature ionic liquids (RTILs). 

Weichbrodt et reported on the use of focused open-vessel microwave-assisted extraction (EOV-MAE) for the determination of organochlorine pesticides in high-moisture samples such as fish. The results were comparable to those with closed-vessel microwave-assisted extraction (CV-MAE) and ASE. The main advantage of FOV-MAE is that the use of Hydromatrix is unnecessary as the solvent mixture of ethyl acetate and cyclohexane allows the removal of water from the sample matrix via azeotropic distillation. 

Microwave-assisted extraction (MAE) is a recent extraction technique, which combines microwave and traditional solvent extraction. The MAE approach have many advantages, such as shorter time, less solvent, higher extraction rate and better products with lower cost. Soxhlet... 

The advantages of ASE over other techniques such as supercritical fluid extraction (SEE) and microwave-assisted extraction (MAE) are not so clear [16,60,62,116]. In fact, SEE features similar extraction times and uses little or no organic solvent. Also, SEE... 

A second approach also using high pressure and temperature is that of microwave assisted extraction. The sample is heated with the extraction solvent in a sealed vessel by microwave energy, as was described for microwave digestion. The temperature can be raised to about 150°C with the already described advantages of high temperature and... 

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. 

The commonly used extraction techniques for organotins are mechanical shaking, ultrasonic extraction, microwave-assisted extraction, or pressurized fluid extraction. Simple mechanical shaking has been used by many testing laboratories, but this has been generally shown to be less effective than the latter three techniques, particularly with respect to recoveries for monosubstituted species. One of the advantages of shaking or ultrasonication is that they... 

Another possibility for essential oils extraction is the use of microwave-assisted extraction (MAE). This methodology appeared to be quite attractive for the isolation of essential oils. The main advantage of using MAE for essential oils extraction is the effective heat transfer that allows quicker times of extraction as compared to classical methods. In the last few years, different applications using microwave energy have been developed. A recent modification of this technique is solvent-free microwave extraction (SEME), where the sample is placed in the reactor inside the microwave oven without any solvent.A cooling system outside the micro-wave oven cool the extract continuously. Einally, the mixrnre of water and essential oil is collected and separated in a vessel. 

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