Polycyclic aromatic hydrocarbons, recovery

At the 95% confidence interval, no significance in terms of the three operating parameters was found when considering the total polycyclic aromatic hydrocarbon recovery. However, recoveries of some individual polycyclic aromatic hydrocarbons were found to be dependent on operating variables. In particular, low operating temperatures of 40 °C were very significant for naphthalene, chrysene and benzo(b)fluoranthene. 

According to the vendor. Microbial Fence has been used to treat groundwater contaminated with polycyclic aromatic hydrocarbons (PAHs) benzene, toluene, ethylbenzene, and xylenes (BTEX) and volatile organic hydrocarbons (VOCs) at petroleum, chemical, and wood treating facilities and manufactured gas plants. Microbial Fence was used alone or in conjunction with soil venting/bioventing, aquifer aeration, pump-and-treat methods, and/or recovery of non-aqueous-phase liquids (NAPLs). 

PAH PAN PBN PCT PES PHREEQC PIC PM PMATCHC PM-10 PM-2.5 PRB PUREX PW PWR PZC Polycyclic aromatic hydrocarbon Peroxyacetylnitrate Peroxybenzoylnitrate Product consistency test Plasma emission spectroscopy pH redox equilibrium calculations (computer program) Product of incomplete combustion Particulate matter Program to manage thermochemical data, written in C++ Particulate matter with an aerodynamic diameter <10 p,m Particulate matter with an aerodynamic diameter <2.5 p,m Powder River Basin Pu-U-recovery-extraction Purex waste Pressurized water reactor Point of zero charge... 

The materials were tested as supports for SPE techniques. Excellent recoveries are observed, exceeding silica-based SPE materials (40). The supports were also investigated for their retention behavior for phenols, alcohols, carboxylic acids, aldehydes, ketones, esters, chloroalkenes, and polycyclic aromatic hydrocarbons (41). 

The relative effects of supercitical carbon dioxide density, temperature, extraction cell dimensions (I.D. Length), and cell dead volume on the supercritical fluid extraction (SFE) recoveries of polycyclic aromatic hydrocarbons and methoxychlor from octadecyl sorbents are quantitatively compared. Recoveries correlate directly with the fluid density at constant temperature whereas, the logarithms of the recoveries correlate with the inverse of the extraction temperature at constant density. Decreasing the extraction vessels internal diameter to length ratio and the incorporation of dead volume in the extraction vessel also resulted in increases in SFE recoveries for the system studied. Gas and supercritical fluid chromatographic data proved to be useful predictors of achievable SFE recoveries, but correlations are dependent on SFE experimental variables, including the cell dimensions and dead volume. 

Saim et al. [96] investigated the interdependence of selected operating parameters on the recovery of 16 polycyclic aromatic hydrocarbons from nine highly contaminated soils, including a range of pressures from 1000-2400 psi, operating temperatures from 40 - 200 ° C, and extraction times from 2 to 16 minutes. 

Polycyclic aromatic hydrocarbons Polycyclic aromatic hydrocarbons co2 Pretreatment of sample with (a) 15% water, (b) 5% (ethylenedinitrilo) tetraacetic acid tetrasodium salt or (c) 50% methanol then extraction with C02 Use of liquid-solid traps compared to analyte trapping 60 - 98% recovery using Na4 EDTA-C02. Only 7 - 63% recovery with C02 alone [133]... 

Andersson, T., T. Pihtsalmi, K. Hartonen, T. Hyotylainem, and M.L. Riekkola. 2003. Effect of extraction vessel geometry and flow homogeneity on recoveries of polycyclic aromatic hydrocarbons in pressurised hot water extraction. Anal. Bioanal. Chem. 376 1081-1088. 

S. B. Hawthorne, D. J. Miller, Extraction and recovery of polycyclic aromatic hydrocarbons from environmental solids using supercritical fluids. Anal. Chem., 59 (1987), 1705-1708. 

It is found that the recoveries of polycyclic aromatic hydrocarbons from soil are similar irrespective of the extraction method used. In addition, similar precision is achieved in both cases. 

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. 

Fig. 2 Supercritical fluid recoveries of polycyclic aromatic hydrocarbons as a function of density and temperature.

Amigo, S.G. Falcon, M.S.G. Yusty, M.A.L. Lozano, J.S. Supercritical liqud extraction of polycyclic aromatic hydrocarbons from liver samples and determination by HPLC-FL. Fresenius J. Anal. Chem. 2000, 367 (6), 572-578. Hawthorne, S.B. Grabanski, C.B. Martin, E. Miller, D.J. Comparison of Soxhlet extraction, pressurized liquid extraction, supercritical fluid extraction and subdritical water extraction for environmental solids Recovery, selectivity and effects on sample matrix. J. Chromatogr., A 2000, 892, 421-433. 

Many researchers reported beneficial effect of plant-microbial consortia on recovery of environmental media polluted with polycyclic aromatic hydrocarbons, synthetic surfactants, petroleum, chloroorganic, nitroaro-matic, phosphoroaromatic compounds, other xenobiotics [1]. 

The Scholl reaction is one of the oldest and most useful C-C coupling reactions, and is often used in the synthesis of polycyclic aromatic hydrocarbons (PAHs). In general, a large amount of metal oxidant (such as FeCls) is employed in this reaction, and chlorinated by-products are produced in many cases. Rathore found that DDQ and protic acid effectively promote the Scholl reaction of various 1,2-diarylbenzenes (86) to give triphenylenes (87) in excellent yields (Scheme 8.40). The advantages of this reaction over typical metal oxidant promoted Scholl reactions are (l) an excess of DDQ is not required (2) no chlorinated by-products are produced and (3) recovery and re-use of reduced hydroquinone DDQ-H2 is possible. The reaction of other diaiyls tethered with methylene and propylene, and the intermolecular reaction also proceeds effectively. Furthermore, the treatment of hexaatylbenzene (88) with DDQ quantitatively affords collonene (89). 

Polycyclic aromatic hydrocarbons are potent immunosuppressive environmental contaminants. Immunotoxic effects of PAHs, which may contribute to their carcinogenic potential, have been established in various animal models and in human immune cells (van Grevenynghe et al., 2004). Inhibition of the production of immunocompetent cells (lymphocytes and monocytes) is likely one of the mechanisms contributing to the immunosuppression due to PAHs. Exposure to PAHs inhibits the differentiation of monocytes into dendritic cells and macrophages it also induces apoptosis of both pre-T cells in the thymus and pre-B cells in the bone marrow, which may account for thymic atrophy and decreased lymphoid cell recovery from the spleen, lymph nodes, and bone marrow in PAH-exposed mice (Lutz et al., 1998 Page et al., 2002). These toxic effects towards precursors of immune cells have been linked, at least in part, to the PAHs metabolism into toxic reactive intermediates triggering apoptosis of pre-B eells (Mann et al., 1999). 

Leoni [366] observed that in the extraction preconcentration of organochlo-rine insecticides and PCB s from surface and coastal waters in the presence of other pollutants such as oil, surface active substances, etc., the results obtained with an absorption column of Tenax-Celite are equivalent to those obtained with the continuous liquid-liquid extraction technique. For non-saline waters that contain solids in suspension that absorb pesticides, it may be necessary to filter the water before extraction with Tenax and then to extract the suspended solids separately. Analyses of river and estuarine sea waters, filtered before extraction, showed the effectiveness of Tenax, and the extracts obtained for pesticide analysis prove to be much less contaminated by interfering substances than corresponding extracts obtained by the liquid-liquid technique. Leoni et al. [365] showed that for the extraction of organic micro pollutants such as pesticides and aromatic polycyclic hydrocarbons from waters, the recoveries of these substances from unpolluted waters (mineral and potable waters) when added at the level of 1 xg/l averaged 90%. 

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