Nonvolatile compounds, soil

Both GC and HPLC columns are expensive, so it is important not to clog them during analysis. GC columns will be clogged by nonvolatile compounds. For these materials, it is important to use HPLC. Samples must also be free of suspended particles that will clog the finely packed HPLC columns. Filtering samples, especially soil extracts, before injection is essential. 

As regards a contaminated soil, this type of analysis may not be possible because the various hydrocarbons cannot be extracted from the sample with equal efficiency. Volatile organic compounds require special procedures to achieve satisfactory recovery from the soil matrix. It thus becomes important to distinguish between those compounds that are considered to be volatile and those that rank as semi- or nonvolatile compounds. 

ICE technology is not designed to remove or treat chlorinated vapors that can produce an offgas stream containing hydrochloric acid. This technology does not treat nonvolatile compounds or heavy metals. Areas with low-permeability soils where minimal flow rates are expected may not be appropriate for this technology. 

In general, the model predicted that polar, nonvolatile compounds will be most effectively transported from soil to fruits, while lipophilic compounds will preferably accumulate from air into fruits. The model results also showed reasonable agreement to experimental data generated from a greenhouse study using " C-labeled TCE and sulfolane (Chard et al., 2006). 

With the exception of picloram and phenols (Fig. 10, Table 3), acidic pesticides are considered nonvolatile from aqueous and soil systems [153]. Some ester formulations of these compounds also behave as herbicides. They do not ionize in solution and are less water-soluble than the acid or salt forms. They are eventually hydrolyzed to acid anions in aqueous and soil systems, but in the ester form are non-ionic and relatively volatile. 

Substituted dinitroanilines (Fig. 10, Table 3) are an important series of selective herbicides commercially introduced in agriculture in the 1960s. Trifluralin is the most prominent member of this series. Nitralin and Benfluralin have also received widespread usage, while Profluralin is a relatively recent herbicide of this class. Dinitro anilines show very low water solubilities. Nitralin and Benfluralin have low vapor pressures and are nonvolatile, while Trifluralin is relatively volatile. All these compounds have been shown to be relatively immobile in soil systems. 

Other examples of nonionic compounds (Fig. 10, Table 3) are the phenyl-amide herbicides (e. g., Diphenamid, moderately water soluble and nonvolatile), thiocarbamate, and carbothioate herbicides (e. g., Thiobencarb, low water solubility, high vapor pressure, relative mobility in soil systems) and benzonitrile herbicides (e.g., Dichlobenil, low water solubility, low vapor pressure, relative immobility in most soils) [151]. 

Grid injection is a commercially available, in situ technology for the treatment of soils contaminated with organic compounds. The technology injects steam to vaporize volatiles and drive out nonvolatiles in a fashion similar to steam stripping. 

The desorption and vapor extraction system (DAVES) uses a low-temperature fluidized bed to remove volatile and semivolatile organics such as polychlorinated biphenyls (PCBs), polynuclear aromatic compounds (PAHs), pentachlorophenol (PCP), volatile inorganics (tetraethyl lead), and some pesticides from soil, sludge, and sediment. The process generally treats waste containing less than 10% total organic contaminants and 30 to 95% solids. The process does not treat nonvolatile inorganic contaminants such as metals. 

The contaminant absorption and recovery (CAR) technology treats volatile organic compounds (VOCs) in gas streams from such processes as soil vapor extraction, air sparging, and air stripping. The contaminated gas stream passes through an absorption solvent, which is a nonvolatile... 

Nonvolatile Organic Compounds Carbamates, Substituted Amides, and Phenylureas in Water and Soil... 

The most widely used solid sample extraction method is Soxhiet extraction. This technique was introduced by Franz Von Soxhiet almost a century ago. Soxhiet extraction is described in U.S.-EPA method 3540 as a procedure for extracting nonvolatile and semivolatile organic compounds from solids such as soils, sludges and wastes. ... 

It is well known that ultrasound has been applied to some organic substrates of environmental interest either to convert them to compounds which are less harmful than the original substrates or to extract species from particulate matter. Sonication is usually recommended for pretreatment of solid environmental samples for the extraction of nonvolatile and semivolatile organic compounds from solids such as soils, sludges and wastes since unsophisticated instrumentation may be used and separations can be performed in a short time using diluted reagents and low temperatures. 

Another process where s-triazines are lost from aquatic and soil systems includes volatizing. Volatility depended upon the vapor pressures of the compounds 126, 128) and the pH of the system (129), Compounds with vapor pressures greater than 1 X 10 mm Hg at 20° C (Table III) vaporized considerably from systems at neutral pH levels. Compounds with vapor pressures ranging from 0.3-0.84 X 10" mm Hg at 20°C (Table III) evaporated less. Compounds with vapor pressures less than 0.3 X 10" mm Hg at 20°C were relatively nonvolatile. Volatility of the compounds was much lower when they had been applied to and adsorbed by soil surfaces instead of metal surfaces (128). 

The acidic pesticides, except for picloram and the phenols, are considered nonvolatile, and losses of the chemicals from aqueous and soil systems are usually insignificant. Anderson et ah (184) found no loss of 2,4-D acid and only a small loss of a-naphthaleneacetic acid when the compounds were applied to glass slides. Schliebe et ah (156) found no loss because of volatizing when chloramben was applied to seven different soils. The vapor pressures of most acid pesticides are low or negligible (Table IV). 

Fig. 2 Persistence of organic chemicals in biosolids-amended soils. A=compounds that are volatile, water soluble, or easily degraded B C=compounds with intermediate sorption potential on biosolids D=compounds whose initial degradation is rate-limited because the microbial population has not acclimated to the compounds and E=compounds that are nonvolatile, relatively water insoluble, and recalcitrant, (after reference [58])...

Ultrasonic LSE is most applicable to the isolation of semivolatile and nonvolatile organic compounds from solid matrices such as soil, sediment, clays, sand, coal tar, and other related solid wastes. U-LSE is also very useful for the disruption of biological material such as serum or tissue. U-LSE can be coupled with solid-phase extraction (SPE) to give a very robust sample preparation method at relatively low cost in comparison to MAE and ASE approaches. The author has utilized U-LSE/SPE to isolate and recover 9,10-dimethyl-l,2-benzanthracene from animal bedding. A 89% recovery was obtained for bedding that was spiked with this polycyclic aromatic hydrocarbon (PAH) of interest to toxicologists (20). An ultrasonic horn and tip are immersed into a mixture of liquid extractant and solid sample and sonicated at some percent of full power for a finite length of time, either continuously or pulsed. 

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