Sediments PCBs. extraction from

PCBs in biological samples are usually extracted by a Soxhlet column and with a nonpolar solvent such as hexane. The sample is first mixed with sodium sulfate to remove moisture. The extraction of PCBs from sediments was tested with sonication, with two sonications interspersed at a 24-h quiescent interval, with steam distillation, or with Soxhlet extraction (Dunnivant and Elzerman 1988). Comparison of the recoveries of various PCB mixtures from dry and wet sediments by the four techniques and the extraction efficiency of four solvents showed that the best overall recoveries were obtained by Soxhlet extraction and the two sonication procedures. In comparisons of solvent systems of acetone, acetonitrile, acetone-hexane (1+1), and water-acetone-isooctane (5+1.5+1), recoveries of lower chlorinated congeners (dichloro- to tetrachloro-) were usually higher with acetonitrile and recoveries of higher chlorinated congeners (tetrachloro- to heptachloro-) extracted with acetone were superior (Dunnivant and Elzerman 1988). The completeness of extraction from a sample matrix does not seem to discriminate against specific isomers however, discrimination in the cleanup and fractionation process may occur and must be tested (Duinker et al. 1988b). 

When other sediments known to support PCB dechlorination were inoculated with PCB-dechlorinating microorganisms and amended with incremental increases of pure petroleum hydrocarbons (0-4 wt%) or 6.2 % petroleum hydrocarbons extracted from Silver Lake sediments, a reduction in both the rate and extent of PCB dechlorination occurred. 

For the river sediment, the use of CO only for the extraction did not achieve high percent recoveries for any of the individual PCB compounds. However, propylene carbonate achieved a nearly complete extraction of each of the PCB compounds from the river sediment with acetonitrile yielding slightly lower recoveries and carbon disulfide achieving the lowest recoveries of the three modifiers examined. It was also interesting to note that there was no preference in terms of the extractability of the monochlorobiphenyl as opposed to the decachlrorobiphenyl regardless of the modifier identity. 

Figure 13.2 MDGC-ECD chromatograms of PCB fractions from sediment samples, demonstrating the separation of the enantiomers of (a) PCB 95, (b) PCB 132, and (c) PCB 149 non-labelled peaks were not identified. Reprinted from Journal of Chromatography, A 723, A. Glausch et al., Enantioselective analysis of chiral polychlorinated biphenyls in sediment samples by multidimensional gas chromatography-electron-capture detection after steam distillation-solvent extraction and sulfur removal , pp. 399-404, copyright 1996, with permission from Elsevier Science.

Another example of ultrasound use is leaching of organic impurities from different kinds of samples. The main analytes of interest are PAHs, which are widespread in soil, sediment, dust, and particulate samples [55]. USE is recommended as a fast, efficient, and direct environmental sample preparation method for determination of PCBs, nitrophenols, pesticides, or polymer additives. Organometallic and biologically active compounds (such as vitamins A, D, and E) present in samples in trace quantities, can be extracted from animal and plant tissues with the aid of ultrasonic wave energy [59]. Table 6.6 presents some typical applications of USE in trace analysis of biological and environmental samples [60]. 

Soil, sediment, and dust samples were prepared in a similar way before analysis. After the pre-cleanup steps and homogenization, FRs were extracted from samples using different solid-liquid extraction techniques. The most commonly used technique was accelerated solvent extraction (ASE), which enables the fast extraction of samples using different solvents such as hexane and dichloromethane [98-100]. Other commonly used techniques for these samples were ultrawave-assisted extraction (UAE) [97], which also enabled quick extraction, and the more time-consuming but very efficient technique, Soxhlet extraction [96]. Some authors have also described less common techniques such as microSPE [95]. There is also information that many FRs that are no longer produced (mainly PCBs and PBDEs) are present in dusts, soils, and sediments in very high amounts, even 390 pg/g [98]. 

Increased amounts of sample call for proportionally increased volumes of supercritical fluid. The sample volume and extraction time can have strong effects in those cases where the analyte concentration in the sample is quite high. Figure 7.8A illustrates the recovery of PCBs from river sediment achieved with pure supercritical CO,. As can be seen, recovery of the target analytes was almost quantitative after 50 min of dynamic extraction of 100 mg of sample on the other hand, quantitative extraction from 1 g of sample was impossible even after 120 min, possibly because the extractant was saturated with PCBs [38]. 

Supercritical Fluids (SFs) allow analytes to be extracted from solid samples, i.e., marine sediments, faster and more efficiently since they have lower viscosity and higher diffusivity than liquid solvents (56). CO2 is the most widely used supercritical fluid with or without a modifier, e.g. methanol and toluene. A very exhaustive discussion on the role of a modifier in the enhancement of the extraction efficiency was recently published (39). Few procedures have been described in the literature based on SFE of organic pollutants from environmental samples, including PCBs and PAHs (39, 41, 56-59). Generally, the extraction is performed... 

PCBs are nonpolar compounds and consequently can be extracted from samples with nonpolar solvents. The efficiency of extraction procedure depends on the nature of the sample, which in turn determines the avaUabihty of native analyte toward the extrachon process. For example, in sediment or soil samples, analytes tend to be very hghtly bound to the matrix and the yield of the extraction may be lower than the same analyte added as spike, so it should be noted that spiking the samples tends to give higher recovery values. In such cases, the availabihty of a reference material may be crucial in order to evaluate the correct recovery of the extraction process. 

Table 3.6 Comparison of Soxhlet Extraction and Different SFE Fluids for the Recovery of PCB Congeners from River Sediment...

Extraction with supercritical CO2 has been recommended for separating a wide variety of analytes, including pesticides, PCBs, vitamin.s, and fragrances from meat. fish, baby food, and animal feed [180]-[185], PAHs. PCBs. PCDO/PCDFs. and other substances have been extracted from soil, fly ash, sediment, air particles, polymers, and plants using supercritical CO2 together with a modifier [186]-[196]. 

Rodriguez (2006) was able to locate numerous sets of data on both the soil turnover rates and depth of soil activity/disturbance for several types of macrofauna. These were converted to particle biodiffusion coefficients and summaries of the data appear graphically in Figure 13.2. Shown in this figure are cumulative probability distributions of this coefficient for earthworms, ants and termites and vertebrates. Included within the earthworm particle data set are four sorbed-phase chemical data points. These Dbs data are for PBCs, which were extracted from concentration profiles using a Fickian diffusion model. The PCB profiles were obtained in soils with abundant earthworm populations. The reader should note that the range of I>bs values for soils is within those for sediments see Figure 13.1 in comparison. 

Results. Various solvent mixtures were tested for extraction efficiency. The test sample was a bone-dry sediment reference material containing 24.6 ppm of Arochlor 1242. This reference material is a real sediment from New Bedford Harbor which was homogenized and carefully assayed for PCB s by the Cincinnati EPA facility. Figure 3 shows recovery of 1242 using (1) hexane alone, (2) hexane and water (1 1), (3) hexane, water, and ethyl ether, (4) ethyl ether and water, (5) ethyl ether, water, and methanol, (6) methanol and hexane (1 1), and (7) water, methanol, and hexane (1 4 5). This last combination appears to give the best recovery. When added in this order to a dry sample, the effect of the water is to wet the sample, thus permitting extraction by methanol. The extracted PCB is partitioned almost exclusively into the hexane from the aqueous methanol. Final recovery is calculated from initial weight and hexane volume. 

Lake sediments Ultrasonic solvent extraction clean-up on Florisil column separation of mi rex and photomi rex from PCBs using charcoal -polyurethane column GC/ECD No data <0.05 ppm 99.9-100 (mi rex) 95.1-99.1 (photomi rex) Chau and Babjak 1979... 

The salient features of the GC-MS data for the neutral extract components separated from PCB contaminated sediment in New Bedford harbor, Massachusetts are given in Fig. 16. The TIC trace indicates a major UCM with super-... 

The first use of supercritical fluid extraction (SFE) as an extraction technique was reported by Zosel [379]. Since then there have been many reports on the use of SFE to extract PCBs, phenols, PAHs, and other organic compounds from particulate matter, soils and sediments [362, 363, 380-389]. The attraction of SFE as an extraction technique is directly related to the unique properties of the supercritical fluid [390]. Supercritical fluids, which have been used, have low viscosities, high diffusion coefficients, and low flammabilities, which are all clearly superior to the organic solvents normally used. Carbon dioxide (C02, [362,363]) is the most common supercritical fluid used for SFE, since it is inexpensive and has a low critical temperature (31.3 °C) and pressure (72.2 bar). Other less commonly used fluids include nitrous oxide (N20), ammonia, fluoro-form, methane, pentane, methanol, ethanol, sulfur hexafluoride (SF6), and dichlorofluoromethane [362, 363, 391]. Most of these fluids are clearly less attractive as solvents in terms of toxicity or as environmentally benign chemicals. Commercial SFE systems are available, but some workers have also made inexpensive modular systems [390]. 

The Soilex process is an ex situ process for extracting polychlorinated biphenyls (PCBs) from soil, sediments or sludge. The soil is mixed with water and an organic solvent to dissolve and remove the PCBs. 

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 Basic Extractive Sludge Treatment (B.E.S.T. ) process is an ex situ solvent extraction technology. The B.E.S.T. process uses one or more secondary or tertiary amines, such as diisopropylamine, to separate contaminants from soil, sediment, and sludge. This technology is applicable to most organics or oily contaminants, including polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs), pesticides, herbicides, dioxins, furans, and other organic compounds. 

In addition to the ability of TGA to quantify the thermal character of soil and sediment organic matter, it has been employed to study the adsorption of volatile organic compounds onto soil and sediment organic matter. For example, Boussehain et al. (1986) used TGA to study alcohol adsorption on charcoals, from which adsorp-tion/desorption isotherms were developed at various temperatures and adsorption models were used to lit experimental data. In addition, Risoul et al. (2002) performed laboratory pilot studies on thermal desorption of polychlorinated biphenyls (PCBs) from a contaminated soil. This study indicated that TGA appears to be a promising tool to determine optimum operating thermal extraction conditions. 

An immediate assay of sediment samples enabled the toxicity due to the presence of inorganic pollutants (metals and sulfates) to be assessed. The assay of organic extracts obtained from the samples enabled the toxicity due to the PAH or PCB content to be determined... 

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