Various Extraction Techniques

For an extraction conducted at a controlled temperature, the oven power output may have less influence on recovery. 

Majority MAE applications have been in the extraction of PAHs, PCBs, pesticides, phenols, and total petroleum hydrocarbons (TPHs) from environmental samples. MAE has also been used in the extraction of contaminants and nutrients from foodstuffs, active gradients from pharmaceutical products, and organic additives from polymer/plastics. Table 3.14 lists some typical applications. Readers interested in the details of MAE applications can find more information in some recent reviews [85-87], 

Lopez-Avila et al. [88] compared MAE, Soxhlet, sonication, and SFE in their ability to extract 95 compounds listed in the EPA method 8250. Freshly spiked soil samples and two SRMs were extracted by MAE and Soxhlet with hexane-acetone (1 1), by sonication with methylene chloride-acetone (1 1), and by SFE with supercritical carbon dioxide modified with 10% methanol. Table 3.16 shows the number of compounds in different recovery ranges obtained by the various techniques. Sonication yielded the highest recoveries, followed by MAE and Soxhlet, whose performances were similar. SFE gave the lowest recoveries. MAE demonstrated the best precision RSDs were less than 10% for 90 of 94 compounds. Soxhlet extraction showed the worst precision only 52 of 94 samples gave RSDs less than 10%. No technique produced acceptable recoveries for 15 polar basic compounds. The recoveries of these compounds by MAE with hexane-acetone at 115°C for 10 minutes (1000 W power) were poor. Consequently, their extraction with MAE was investigated using acetonitrile at 50 and 115°C. Ten of the 15 compounds were recovered quantitatively ( 70%) at 115°C. 

Analytes Matrix Vessel Type Solvents Extraction Conditions Recovery (%) RSD (%) Reference 

PAHs SRMs, spiked, and real soil samples Open 20 mL of acetone-hexane (1 1) 1-g sample, 10 min 96-100 7 83 

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Table 3.4 summarises the main characteristics of a variety of sample preparation modes for in-polymer additive analysis. Table 3.5 is a short literature evaluation of various extraction techniques. Majors [91] has recently reviewed the changing role of extraction in preparation of solid samples. Vandenburg and Clifford [4] and others [6,91-95] have reviewed several sample preparation techniques, including polymer dissolution, LSE and SEE, microwave dissolution, ultra-sonication and accelerated solvent extraction. 

Nematode population Various extraction techniques Indicates soil food web functioning, species richness, and abundance spatially variable time-consuming Blair et al. (1996)... 

Miege C, Dugay J, Hennion MC. Optimization, validation and comparison of various extraction techniques for the trace determination of polycyclic aromatic hydrocarbons in sewage sludges by liquid chromatography coupled to diode-array and fluorescence detection. J. Chromatogr. A 2003 995 87-97. 

David and Seilier [1] compared the efficiencies of various extraction techniques including supercritical fluid [2], high pressure solvent and Soxhlet extraction for the removal of organophosphorus hydraulic fluids from soil. High pressure solvent extraction was at temperatures up to 200°C and pressures up to 170 bar was the favoured technique. Extraction efficiencies were similar in all three methods, but the favoured method was more rapid and cheaper to operate. 

Hartonen et al. [286] have reported various extraction techniques for organochlorine insecticides in soils. Trapping efficiencies were reported for organochlorine insecticides, selected polychlorinated benzenes, polybromi-nated biphenyls, and polybrominated diphenyl ethers. 

Figure 1.5.1 Schematic diagram of various extraction techniques.

Table 3.15 summarizes the advantages and disadvantages of various extraction techniques used in the analysis of semivolatile organic analytes in solid samples. They are compared on the basis of matrix effect, equipment cost, solvent use, extraction time, sample size, automation/unattended operation, selectivity, sample throughput, applicability, filtration requirement, and the need for evaporation/concentration. The examples that follow show the differences among these techniques in real-world applications. 

Table 3.15. Advantages and Disadvantages of Various Extraction Techniques...

Berman discusses the difficulty of extracting the proteins of vision from the retinal outer segments based on the assumption that the chromophores of vision are an integral part of the protein rhodopsin235. She discusses the various extraction techniques based on this assumption and the resulting percentage compositions reported in the literature. 

The first chapter gives a short description of each of the techniques described in the book. This section is mainly intended for people who are new to the field. Those already familiar with the various extraction techniques can go straight to the second chapter. 

Various extraction techniques are applied to isolate EDCs in aqueous samples, such as liquid-liquid extraction (LEE), solid-phase extraction (SPE), and solid-phase microextraction (SPME). LEE is frequently used in the extraction of EDCs with water immiscible organic solvents, most... 

Various extraction techniques have been applied and reported in literature for PCB analysis. Such methods include microwave-assisted headspace solid-phase microextraction of PCBs in aqueous samples (Shu et al. 

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. 

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