Focused microwave-assisted Soxhlet extraction

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 ... 

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,... 

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... 

Prados-Rosales, R. C., Herrera, M. C., Luque-Garcia, J. L., and Luque de Castro, M. D., Study of the feasibility of focused microwave-assisted Soxhlet extraction of A-methylcarbamates from soil, J. Chromatogr. A, 953, 133-140, 2002. 

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, 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. 

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. 

Two main types of MAE systems are commercially available, in both cases agitation is provided during extraction to improve the mass transfer phenomenon. In closed extraction vessels, extraction is performed under controlled pressure and temperature. In focused microwave-assisted solvent extraction (FMASE), only a part of the extraction vessel containing the sample is irradiated with microwaves. Instrumental setups like Soxwave combine both the features of Soxhlet and the advantages of microwave, thus making extraction an even more attractive alternative to traditional solid—liquid extraction. 

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. 

Microwave-assisted extractions (MAE) can be performed in open (focused MAE) or closed (pressurized MAE) flasks. This technique is commonly used for extractions from complex and difficult sample matrices, replacing time- and solvent-intensive Soxhlet extractions or hydrodistillations.46 MAE is also widely applied to environmental samples, for example, for extracting polycyclic aromatic hydrocarbons (PAH) from soil, methylmercury from sediments, and trace metals and pesticide residues from plant material47 48 The use of microwave treatment instead of hydrodistillation offers a solvent-free separation technique essential oils are heated and dry-distilled 46... 

Morales-Munoz, S., J.L. Luque-Garcia, and M.D. Luque de Castro. 2004. Screening method for linear alkylbenzene sulfonates in sediments based on water Soxhlet extraction assisted by focused microwaves with on-line preconcentration/derivatization/detection. J. Chromatogr. A 1026 41 —46. 

This chapter covers techniques for the extraction of semivolatile organics from solid matrices. The focus is on commonly used and commercially available techniques, which include Soxhlet extraction, automated Soxhlet extraction, ultrasonic extraction, supercritical fluid extraction (SFE), accelerated solvent extraction (ASE), and microwave-assisted extraction (MAE). The underlying principles, instrumentation, operational procedures, and selected applications of these techniques are described. In a given application, probably all the methods mentioned above will work, so it often boils down to identifying the most suitable one. Consequently, an effort is made to compare these methodologies. 

The focus in Chapters 7 and 8 is on the specific sample preparation approaches available for the extraction of organic compounds from environmental matrices, principally soil and water. Chapter 7 is concerned with the role of Soxhlet, ultrasonic and shake-flask extraction on the removal of organic compounds from solid (soil) matrices. These techniques are contrasted with newer developments in sample preparation for organic compound extraction, namely supercritical fluid extraction, microwave-assisted extraction and pressurized fluid extraction. Chapter 8 is arranged in a similar manner. Initially, details are provided on the use of solvent extraction for organic compounds removal from aqueous samples. This is followed by descriptions of the newer approaches, namely solid-phase extraction and solid-phase microextraction. 

For practical reasons, classical procedures are continuously upgraded to get improvements in terms of reliability and performance. Such an approach relates, for example, to the conventional Soxhlet extraction assisted by focused microwaves (FMSE). The main factors affecting extraction efficiency are microwave power, irradiation time, volume of the extractant, and number of cycles. The result, in terms of extracted mass and repeatability is similar to the classical method. In addition, there is a significant reduction in the total time taken for the process and far less amount of extractant is consumed. Organo-chlorine pesticides (OCPs) and related residues have been successfully isolated from sunflower seeds by means of FMSE. Comparison with the ISO 659-1988... 

In this context, studies about the development of relevant analytical methods allowing the detection of pesticide residues in VOO are usually focused on an optimization of the various steps of the analysis process, namely extraction, clean-up, identification, and quantitation of pesticide content. The common extraction methods are Soxhlet extraction, microwave-assisted extraction (MAE), supercritical fluid extraction (SEE), and accelerated solvent extraction (ASE). Cleanup methods include SPE, matrix solid-phase dispersion (MSPD), and gel permeation chromatography (GPC). 

The solvent technique for concentrating surfactants is not discussed here. See Ref. [40] for details. Morales-Munoz et al. discuss a screening method for LAS in sediments. It is based on water Soxhlet extraction assisted by focused microwaves. The extractor is coupled with an online preconcentrator/derivatization/detection manifold through a flow injection interface [107]. 

---