Dynamic microwave-assisted extraction

Chen L, Jin H, Ding L, Zhang H, Li J, Qu C and Zhang H 2008. Dynamic microwave-assisted extraction of flavonoids from Herba Epimedii. Sep Purif Technol 59(1) 50—57. 

Fig. 5.5. (A) Scheme of a flow digestion system and the principle of pressure equilibration A pressure reactor, B heating zone, C cooling zone, D digestion coil, E cooling device, F connection for gas supply, G restrictor tube, H collector vial, I temperature sensor, J high-pressure pump, K injection valve, L sample loop, M sample, N and O peristaltic pumps. (Reproduced with permission of the American Chemical Society.) (B) Manifold for dynamic microwave-assisted extraction I solvent, 2 pump, 3 microwave oven, 4 extraction chamber, 5 temperature set-point controller, 6 thermocouple, 7 fluorescence detector, 8 recording device, 9 restrictor, 10 extractor. (Reproduced with permission of Elsevier.)...

L.-G. Chen, L. Ding, H.-R. Zhang, J. Li, Y.-T. Wang, X.-P. Wang, C.-L. Qu, H.-Q. Zhang, Dynamic microwave-assisted extraction coupled with on-line spectrophotometric determination of safflower yellow in Flos Carthami, Anal. Chim. Acta 580 (2006) 75. 

Ericsson, M. and Colmsjo, A., Dynamic microwave-assisted extraction coupled online with SPE and large-volume injection gas chromatography determination of organophosphate esters in air samples. Anal. Chem., 75, 1713-1719, 2003. 

Figure 2 (A) Conventional Soxhiet extractor. (B) Focused microwave-assisted Soxhiet extractor from Prolabo. (Reproduced with permission from Ericsson M and Colmsjo A (2000) Dynamic microwave-assisted extraction. Journal of Chromatography 897 279 Elsevier.)...

Then L, Ding L, Yu A, Yang R, Wang X, Li J, Jin H, Zhang H (2007) Continuous determination of total flavonoids in Platycladus orientalis (L.) Franco by dynamic microwave-assisted extraction coupled with on-line derivatization and ultraviolet-visible detection. Anal Chim Acta 596 164—170... 

The mode of extraction for PAHs is highly dependent on the matrix. For solid-based matrices such as food samples, sediments, soil, marine organisms, etc. extraction methods such as Soxhlet extraction with nonpolar solvent [35 6], hollow fiber membrane solvent microextraction (HFMSME) [10], pressimzed hquid extraction (PLE) [37,38], sonication extraction [3], microwave-assisted extraction (MAE) [3], supercritical fluid extraction, (SEE) [39], accelerated solvent extraction (ASE) [40], cold extraction [41], soxtec extraction [42], microwave-assisted alkaline saponification (MAAS) [43], dynamic microwave-assisted extraction (DMAE) [44], add-induced cloud point extraction (ACPE) [45], methanolic saponification extraction (MSE) [7], etc. are employed. Of all these, Soxhlet extraction is the most common for solid samples and has achieved excellent extraction with high-level recovery but its setback is the high consmnption of solvent and time associated with it. 

Fig. 5.8. (A) General scheme of a dynamic focused microwave-assisted extractor. (B) Experimental set-up used to integrate microwave-assisted extraction with the subsequent steps of the analytical process. (1) Leaching step CT controller, MO microwave oven, S sample, R condenser, WR water reservoir, TCPP two-channel piston pump, ER extract reservoir, SV switching valve. (2) Clean-up/preconcentration step M methanol, A air, B buffer, PP peristaltic pump, F filter, EL elution loop, MC mini-column, R retention direction, E elution direction, 1V1-1V3 injection valves, W waste. (3) Individual separation-detection step HPIV high-pressure injection valve, AC analytical column, DAD diode array detector, SR solvent reservoirs.

An essential oil (EO) is internationally defined as the product obtained by hydro-, steam-, or dry-distillation of a plant or of some of its parts, or by a suitable mechanical process without heating, as in the case of Citrus fruits (AFNOR, 1998 Council of Europe, 2010). Vacuum distUladon solvent extraction combined offline with distillation simultaneous distillation extraction supercritical fluid extraction microwave-assisted extraction and hydro-distiUation and static, dynamic, and high concentration capacity headspace sampling are other techniques used for extracting the volatile fraction from aromatic plants, although the products of these processes cannot be termed EOs (Faleiro and Miguel, 2013). 

LLE, liquid-liquid extraction MAE, microwave-assisted extraction SEE, solid-phase extraction SPME, solid-phase microextraction LPME, liquid-phase microextraction SOME, single-drop microextraction D-LLLME, dynamic liquid-liquid-liquid microextraction SEE, supercritical fluid extraction MIP, molecularly imprinted polymers sorbent SPMD, device for semipermeable membrane extraction PDMS, polydimethylsiloxane coated fiber PA, polyacrylate coated fiber CW-DMS, Carbowax-divinylbenzene fiber PDMS-DVB, polydimethylsiloxane divinylbenzene fiber CAR-PDMS, Carboxen-polydimethylsiloxane coated fiber DVB-CAR-PDMS, divinylbenzene Carboxen-polydimethylsiloxane coated fiber CW-TPR, Carbowax-template resin HS-SPME, headspace solid-phase microextraction MA-HS-SPME, microwave-assisted headspace-solid-phase microextraction HEM, porous hollow fiber membrane PEl-PPP, polydydroxylated polyparaphenylene. 

Dynamic versus Static SFE Accelerated Solvent Extraction (ASE) Microwave-Assisted Extraction (MAE) Membrane-Based Extractions Pyrolysis Automation Derivatization Thermal Desorption... 

Dynamic systems for high-pressure microwave treatment were developed much later than open-vessel systems. Operating under a high pressure reduces the flexibility afforded by working at atmospheric pressure. However, some recently developed devices allow microwave-assisted high-pressure digestion and extraction in a dynamic manner [33,34]. 

---