Focused microwave-assisted Soxhlet

FMASE Focused microwave-assisted Soxhlet GPEC Gradient polymer elution... 

Three factors, namely (1) irradiation power as a percentage, (2) irradiation time in seconds and (3) number of cycles, are used to study the focused microwave assisted Soxhlet extraction of olive oil seeds, the response measuring the percentage recovery, which is to be optimised. A central composite design is set up to perform the experiments. The results are as follows, using coded values of the variables ... 

As noted earlier, not all open-vessel systems (viz. those that operate at atmospheric pressure) are of the focused type. A number of reported applications use a domestic multi-mode oven to process samples for analytical purposes, usually with a view to coupling the microwave treatment to some other step of the analytical process (generally the determination step). Below are described the most common on-line systems used so far, including domestic ovens (multi-mode systems) and open-vessel focused systems, which operate at atmospheric pressure and are thus much more flexible for coupling to subsequent steps of the analytical process. On the other hand, the increased flexibility of open-vessel systems has promoted the design of new microwave-assisted sample treatment units based on focused or multi-mode (domestic) ovens adapted to the particular purpose. Examples of these new units include the microwave-ultrasound combined extractor, the focused microwave-assisted Soxhlet extractor, the microwave-assisted drying system and the microwave-assisted distillation extractor, which are also dealt with in this section. Finally, the usefulness of the microwave-assisted sample treatment modules incorporated in robot stations is also commented on, albeit briefly as such devices are discussed in greater detail in Chapter 10. 

Focused microwave-assisted Soxhlet extractor The first prototype of a focused microwave-assisted Soxhlet extractor was designed by Luque de Castro et al. and... 

Focused Microwave assisted Soxhlet Extraction (FMASE) Water is used as the extractant in the application of focused microwaves to enhance the extraction. (9)... 

Luque-Garcia, Focused microwave-assisted Soxhlet extraction, J.L and Luque-Castro, M.D., Anal. Chem., 2001, 73, 5903. 

The improvements in Soxhlet extractions are high-pressure Soxhlet extraction (HPS), automated Soxhlet extraction (Soxhlet HT and Buchi B811) and focused microwave-assisted Soxhlet extraction (Soxwave and FMASE) as shown by Luque de Castro MD and Garcia-Ayuso in 1998. The solvents used for extraction are polar species (dimethyl formamide,... 

FIGURE 2.17 Automated focused microwave-assisted Soxhlet extractor. (Reprinted from Luque-Garcfa, J. L. and Luque de Castro, M. D., J. Chromatogr. A, 998, 21-29, 2003. With permission from Elsevier.)... 

One useful aspect of microwave systems with open vessels is that they allow direct adaptation of already existing sample preparation methods. Of particular interest for chromatography is the focused microwave-assisted Soxhlet extractor (Figure 2.17 and Figure 2.27). It is based on the same principles as a conventional Soxhlet extractor but is modified to facilitate accommodation of the sample-cartridge compartment in the irradiation zone of a microwave oven. The modification... 

New developments in Soxhlet extraction have been applied to the analysis of PAHs in soils and sediments. " Focused Microwave-Assisted Soxhlet Extraction (FMASE) uses focused microwave irradiation to achieve agitation in the sample. The application of microwaves drastically reduces extraction time ( 1 h) and solvent use. Recoveries of PAHs were reported to be 11 to 101 % in the extraction step and no filtering was necessary prior to analysis. 

LLE liquid-liquid extraction SPE solid-phase extraction SPM solid-phase microextraction MAE microwave-assisted extraction SEE supercritical fluid extraction FMASE focused microwave-assisted Soxhlet extraction PSDB polystyrene-divinylbenzene NVPDB A-vinylpyrrolidane-divinylbenzene SPE solid-phase extraction LLE liquid-liquid extraction GPC gel permeation chromatography OPA f -phthalaldehyde reagent TAD thermally assisted desorption FI flow injection... 

Garcia-Ayuso, L. E., Sanchez, M., Fernandez de Alba, A., and Luque de Castro, M. D., Focused microwave-assisted Soxhlet an advantageous tool for sample extraction. Anal. Chem., 70, 2426-2431, 1998. 

The increased flexibility of open-vessel systems has promoted the design of new microwave-assisted sample treatment units based on focused or multi-mode (domestic) ovens adapted to the particular purpose. Regarding MAE, examples of these new units include the microwave-ultrasound combined extractor and the focused microwave-assisted Soxhlet extractor. 

One of the most interesting fields of application of MAE in food analysis is the extraction of lipids. This step, traditionally performed with conventional Soxhlet extraction, has been performed with the focused microwave-assisted Soxhlet extractor prototype of Figure 2B. Extraction of oil from olives, srm-flower seeds, and soyabeans extraction of the lipid fraction of dairy products (milk and cheese) and extraction of fatty acids from precooked and sausage foods have significant advantages over conventional methods, including dramatically reduced extraction times, lower degradation of thermolabile analytes, and acceleration of other analytical steps such as hydrolysis in milk samples, in addition to completeness of analyte extraction, which is not always achieved with conventional methods. 

Priego-Lopez, E. Velasco, J. Dobarganes, M.C. Ramis-Ramos, G. de Castro, M.D.L. Focused microwave-assisted Soxhlet extraction an expeditive approach for the isolation of lipids from sausage products. Food Chem. 2003, 83 (1), 143-149. 

In Figure 7.53 a flow-injection interface for fluorometric monitoring of focused microwave-assisted Soxhlet extraction is represented [195]. This assembly allows real-time online monitoring of the PAHs extracted from solid samples in each Soxhlet cycle and provides qualitative and semi-quantitative information from natural and spiked samples. The method has been applied to a certified reference material (CRM 524, BCR, industrial soil/organics) for quality assurance/validation. The proposed technique is as efficient as conventional Soxhlet to extract PAHs from soils but with a drastic reduction of both extraction time and organic solvent disposal. 

Flow injection interface for fluorometric monitoring of focused microwave-assisted Soxhlet extraction. IV injection valve PV pressure valve RC reaction coil V solenoid valve. 

Garcia-Ayuso, LJi., Velasco, J., Dobarganes, M.C., and Luque de Castro, M.D., Accelerated extraction of the fat content in cheese using a focused microwave-assisted Soxhlet device, J. Agric. Food Chem., 47, 2308-2315, 1999. 

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