Vapor phase organic extractable from

Figure 3. Reconstructed ion chromatograms from GC/MS analysis of vapor phase organic extractable from Tenax (upper trace) and dichloromethane extractables from glass fiber Tenax filter (lower trace). Samples of the raw gas collected after the cyclone. A 25 m OV-101 quartz capillary column was used in a Finnigan model 4023 gas chromatograph mass spectrometer. Temperature program was 2 min at 50°C, 5°C/min to 270°C with 15 min at 270 C.

Multiphase extraction uses a vacuum system to remove various combinations of contaminated groundwater, separate-phase petroleum product, and vapors from the subsurface. The system lowers the water table around the well, exposing more of the formation. Contaminants in the newly exposed vadose zone are then accessible to vapor extraction. Once above ground, the extracted vapors or liquid-phase organics and groundwater are separated and treated. 

The two-phase vacuum extraction (TPVE) technology allows for the in situ remediation of soils and groundwater contaminated with volatile organic compounds (VOCs). Two-phase vacuum extraction is similar to conventional vapor extraction in the equipment required, with the exception that it is designed to actively remove contaminated groundwater from the extraction well along with the vapor-phase contamination. 

Reclaim is a passive, in situ technology that uses a hydrophobic porous polymer to attract, adsorb, and concentrate petroleum hydrocarbons and volatile organic compounds (VOCs) from soils and/or groundwater. Reclaim is considered a passive treatment technology because it requires no mechanical equipment remediation consists of placing polymer-filled canisters in recovery wells and allowing the containers to attract and adsorb organic contaminants. Reclaim canisters are then recycled and contaminants recovered for analysis and/or disposal. This polymer extracts contaminants whether they are in liquid phase, vapor phase or dissolved phase in water. 

In addition to the examples discussed above, a number of other xenobiotics are measured by their phase I reaction products. These compounds and their metabolites are listed in Table 20.1. These methods are for metabolites in urine. Normally, the urine sample is acidified to release the phase I metabolites from phase II conjugates that they might have formed, and except where direct sample injection is employed, the analyte is collected as vapor or extracted into an organic solvent. In some cases, the analyte is reacted with a reagent that produces a volatile derivative that is readily separated and detected by gas chromatography. 

The column extraction is based on the following principle the water sample is distributed as a film at the contact with the adsorbent. Afterwards, the elution with immiscible water solvents is performed (e.g. diethylether, ethylacetate or chlorinated solvents). All the lyphophyle pollutants are extracted from the aqueous into the organic phase. During the process the aqueous phase remains on the stationary phase and emulsion formation is no longer possible. The extract can be vaporized and the pollutants will be analyzed. 

Many of the isomeric Cg through Cgg alkanes have been identified in the organic solvent-soluble extracts from one or more of the major tobacco types (flue-cured, burley. Oriental, Maryland). Their presence in tobacco smoke is the result of their volatilization during the puff and smolder phases of the smoking process and subsequent direct transfer from the tobacco to its MSS and sidestream smoke (SSS). The bulk of these higher alkanes are found in the particulate phase of the smoke aerosol with traces of the lower ones (Cg-Cij) in the vapor phase. 

Analytes are introduced into GC colmtms with several techniques. An ahquot of a relatively concentrated vapor or air sample— for example, from a plastic bag or a canister—can be introduced into a short section of tubing of known volume, called a sample loop, and subsequently pinged with carrier gas into the GC colurmt Volatile analytes in ambient air samples in a canister or trapped on a solid phase adsorbent are usually concentrated and focused in a cryogenic trap or a secondary adsorbent trap, then thermally vaporized into the GC carrier gas stream. However, in some analytical methods, volatiles trapped on an absorbent are thermally desorbed directly into the GC colunm. Aliquots of organic solvent extracts from various aqueous and solid samples are usually injected with a syringe into the carrier gas stream in a heated injection port. Both manual and antomated syringe injection systems (autoinjectors) are used and the latter are generally very reliable, precise, and have the capacity to process many samples unattended. 

The preferred technique for sampling organic vapors is collection on a porous sorbent by the van der Waals forces of adsorption (particularly the London dispersion force), with later desorption and instrumental analysis. The rate of adsorption at the sorbent surface is extremely fast and is not normally considered a rate-controlling step, and the adsorption equilibrium is normally shifted far enough in the direction of the adsorbed phase that the concentration at the sorbent surface can be regarded as insignificant. All molecules that arrive at the surface are therefore adsorbed. The adsorbed vapors are extracted from the sorbent by means of a solvent or heat, and analysis is normally carried out by gas chromatography (GC), or less often by LC. 

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