Extraction volatile organics from

The fluid injection with vacuum extraction (FIVE system) technology uses injection wells to extract volatile organic compounds (VOCs) (generally resulting from a spill) from groundwater... 

In bench-scale testing, SCDE has demonstrated the ability to extract volatile organic compounds (VOCs) and semivolatUe organic compounds (SVOCs) including polychlorinated biphenyls (PCBs) from various substrates. 

As discussed in this book, certain sample preparation techniques are clearly more appropriate for volatile compounds than for semivolatile and nonvolatile compounds. In this chapter we concentrate on extraction methods for semivolatile organics from liquids. Techniques for extraction of volatile organics from solids and liquids are discussed in Chapter 4. 

Membrane pervaporation (permselective evaporation of liquid molecules) is the term used to describe the extraction of volatile organics from an aqueous matrix to a gas phase through a semipermeable membrane. 

Solvents may also be used for desorption of porous polymer traps as discussed by Schaefer ( 23). Recently Parliment (2jl) described a micro solvent extraction apparatus for desorbing volatile organics from C-18 or Tenax traps. Less than a milliliter of solvent is used to desorb the volatiles from the trap, and the solvent is recycled to achieve complete desorption. 

Extraction of Volatile Organics from Aqueous Solutions... 

Soxhlet extraction Semi-volatile and non-volatile organics from soils, relatively dry sludges and solid wastes Considered a rugged extraction method because it has very few variables that can adversely affect extraction recovery... 

FIGURE 3.3 (a) Glass flask for extracting volatile organic compounds from water samples. 

Adjusting the Analyte s Concentration Analytes present at concentrations too small to give an adequate signal need to be concentrated before analyzing. A side benefit of many of the extraction methods outlined earlier is that they often concentrate the analytes. Volatile organic materials isolated from aqueous samples by a purge and trap, for example, can be concentrated by as much as 1000-fold. 

Commercial polystyrenes are normally rather pure polymers. The amount of styrene, ethylbenzene, styrene dimers and trimers, and other hydrocarbons is minimized by effective devolatilization or by the use of chemical initiators (33). Polystyrenes with low overall volatiles content have relatively high heat-deformation temperatures. The very low content of monomer and other solvents, eg, ethylbenzene, in PS is desirable in the packaging of food. The negligible level of extraction of organic materials from PS is of cmcial importance in this appHcation. 

A U.S. EPA study (41) showed that soil vapor extraction (SVE) is an effective treatment for removing volatile contaminants from the vadose zone. Sandy soils are more effectively treated than clay or soils with higher organic content because higher air flows are possible in sand and clays—organic soils tend to adsorb or retain more contaminants. Removal of volatiles is rapid in the initial phase of treatment and thereafter decreases rapidly thereafter-an important consideration in the design of air emissions control over the life of the project. 

Livingston, A.G., Freitas dos Santos, L.M., Extraction and Biodegradation of a Toxic Volatile Organic Compound (1,2 dichloroethane) from Wastewater in a Membrane Bioreactor, Applied Microbiology and Biotechnology, v.42, pp.421-431, 1994. 

The most commonly used remediation technique for the recovery of organic contaminants from ground water has been pump- and-treat, which recovers contaminants dissolved in the aqueous phase. In this regard, the application of carbon adsorption has found extensive, but not exclusive use. Vacuum extraction (also called soil venting) has also become popular for removal of volatile organic contaminants from the unsaturated zone in the gaseous phase. Both of these techniques can, in the initial remediation phase, rapidly recover contaminants at concentrations approximately equal to the solubility limit (pump-and-treat), or the maximum gas phase concentration of the contaminant (vacuum extraction). The... 

The study of biochemical natural products has also been aided through the application of two-dimensional GC. In many studies, it has been observed that volatile organic compounds from plants (for example, in fruits) show species-specific distributions in chiral abundances. Observations have shown that related species produce similar compounds, but at differing ratios, and the study of such distributions yields information on speciation and plant genetics. In particular, the determination of hydroxyl fatty acid adducts produced from bacterial processes has been a successful application. In the reported applications, enantiomeric determination of polyhydroxyl alkanoic acids extracted from intracellular regions has been enabled (45). 

Volatile impurities in an ionic liquid may have different origins. They may result from solvents used in the extraction steps during the synthesis, from unreacted starting materials from the allcylation reaction (to form the ionic liquid s cation), or from any volatile organic compound previously dissolved in the ionic liquid. 

Headspace analysis has also been used to determine trichloroethylene in water samples. High accuracy and excellent precision were reported when GC/ECD was used to analyze headspace gases over water (Dietz and Singley 1979). Direct injection of water into a portable GC suitable for field use employed an ultraviolet detector (Motwani et al. 1986). While detection was comparable to the more common methods (low ppb), recovery was very low. Solid waste leachates from sanitary landfills have been analyzed for trichloroethylene and other volatile organic compounds (Schultz and Kjeldsen 1986). Detection limits for the procedure, which involves extraction with pentane followed by GC/MS analysis, are in the low-ppb and low-ppm ranges for concentrated and unconcentrated samples, respectively. Accuracy and precision data were not reported. 

A reference to the versatility of ionic liquids was made in Section 4.2.3. These liquids are a new class of solvents which do not have any problems associated with volatile organic liquids. Rogers et al. (1999) have used butylmethylimidazolium hexafluorophosphate to extract a benzene derivative from water. 

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