Extraction methods, effects

Leaching Cycle and Contact Method As is true generally, the choice between continuous and intermittent operation is largely a matter of the size and nature of the process of which the extraction is a part. The choice of a percolation or solids-dispersion technique depends principally on the amenability of the extraction to effective, sufficiently rapid percolation. 

Garimella et investigated the effect on trifluralin recovery of different extraction methods. A supercritical fluid extraction (SEE) procedure for the isolation of the analytes from the matrices with a commercial SEE system (Dionex Model 703)... 

SFE. SFE has been established as the extraction method of choice for solid samples. The usefulness of SFE for soil samples has been demonstrated for carbamate,organophosphorus and organochlorine pesticides. However, SFE is more effective in extracting nonpolar than polar residues. In order to obtain a greater extraction efficiency for the polar residues of imidacloprid, the addition of 20% methanol as modifier is required. Extraction at 276 bar and 80 °C with a solvent consisting of supercritical carbon dioxide modified with methanol (5%) for 40 min gives a recovery of 97% (RSD = 3.6%, n = 10). It is possible to use process-scale SFE to decontaminate pesticide residues from dust waste. ... 

Freitag and John [96] studied rapid separation of stabilisers from plastics. Fairly quantitative extraction (>90% of the expected content) of stabilisers from a powdered polymer was achieved by MAE within 3 to 6 min, as compared to 16 h of Soxhlet extraction for the same recovery. MAE and Soxhlet extraction have also been compared in the analysis of cyclic trimer in PET [113]. On the other hand, Ganzler et al. [128] compared the extraction yields for various types of compounds from nonpolymeric matrices for microwave irradiation with those obtained by the traditional Soxhlet or shake-flask extraction methods. Microwave extraction was more effective than the conventional methods, in particular in the case of polar compounds. As expected, the efficiency of the former is high especially when the extraction solvents contain water. With the high dipole moment of water, microwave heating is more... 

Isolation may occur by liquid-solid interaction (extraction, dissolution) or heat (thermal, pyrolytic, laser). Extraction methods easily handle qualitative screening for low- to medium-MW compounds fail for high-MW components or polymer-bound functionalities and are less reliable quantitatively (analyte dependent). When applicable, dissolution methods suffer from sensitivity, because of the dilution effect on account of the polymer. In-polymer analysis performs well for qualitative screening, but is as yet not strongly performing for quantitative analysis, except for some specific questions. 

The vacuum extraction method has been effectively applied to removing VOCs with low organic carbon content from well-drained soil, although it may also be effective for finer and wetter soils, but with comparatively slower removal rates. There are generally significant differences in the air permeability of various strata, which can influence process performance. Contaminants with low vapor pressure or high water solubilities are difficult to remove. 

Another characteristic to take into account is that ATP is an endogenous component of the cells, both somatic and bacterial. Therefore, an extraction step must to be included in the assay protocol it is very simple and quick to perform. Several extraction methods have been reported, both physical and chemical, such as heating and the use of surfactants, trichloroacetic acid, and organic solvents [89, 120, 121], The chemical methods are generally preferred the addition of a surfactant can be effective in most cases. The use of mild or strong extraction... 

To determine the various species and their concentrations in soil, many selective, semiselective, and sequential extraction methods have been developed. Species associated with various components in soil can be extracted with varying effectiveness (see Chapters 11 and 12). Thus, metal cations that are in solution, exchangeable, weakly held, or associated with carbonate and with... 

Askari et al. [15] have compared purge and trap, methanol immersion and hot solvent extraction methods for the determination of volatile organic compound in aged soil. These workers found that hot solvent extraction is much more effective than the US Environmental Protection Agency approved purge and trap technique [7, 8]. 

Muller, C., Schafer, P., Stortzel, M., Vogt, S., and Weinmann, W. (2002). Ion suppression effects in liquid chromatography-electrospray-ionization transport-region collision induced dissociation mass spectrometry with different serum extraction methods for systematic toxicological analysis with mass spectra libraries. /. Chromatogr. B 773, 47— 52. 

The actual values of gjj determined experimentally depend, of course, on the method used to extract the effective fej and 2 from the titration curve. Figure 4.32 shows the BI (transformed into -20 + 2 to conform with the titration curve, see Appendix G) and its derivative, along with the corresponding titration curves for the values of k, Ajj, and k with = 1/2. It is clear that the BI has four... 

The results discussed above suggest that an adjustment in the rate of mixing in the formation of microspheres by solvent extraction method is not effective in achieving narrow dispersion of diameters of microspheres. 

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