Polyaromatic hydrocarbons, from

This publication provides several examples of the use of solid-phase extractions for separating analytes from their matrices. Some of the examples included are caffeine from coffee, polyaromatic hydrocarbons from water, parabens from cosmetics, chlorinated pesticides from water, and steroids from hydrocortisone creams. Extracted analytes maybe determined quantitatively by gas (GC) or liquid chromatography (LG). 

Polyaromatic hydrocarbons absorb strongly to humus and other soil components, rendering these contaminants difficult to remove by thermal, physical, or chemical means, and unavailable for biodegradation. To desorb polyaromatic hydrocarbons from soil, surfactant flooding processes and soil-washing processes or treatments to enhance the biodegradation of polyaromatic hydrocarbons have been considered. 

Reindt and Hoffler [50] optimized parameters in the supercritical fluid extraction of polyaromatic hydrocarbons from soil. These workers used carbon dioxide -8% methanol for extraction and obtained 88-101% recovery of polyaromatic hydrocarbons in the final high-performance liquid chromatography. 

Barnabas et al. [51] have discussed an experimental design approach for the extraction of polyaromatic hydrocarbons from soil using supercritical carbon dioxide. They studied 16 different polyaromatic hydrocarbons using pure carbon dioxide and methanol modified carbon dioxide. The technique is capable of determining down to lOOmg kgy1 polyaromatic hydrocarbons in soils. 

Lopez-Avila et al. [59] used microwave assisted extraction to assist the extraction of polyaromatic hydrocarbons from soils. Another extraction method was described by Hartmann [60] for the recovery of polyaromatic hydrocarbons in forest soils. The method included saponification of samples in an ultrasonic bath, partitioning of polyaromatic hydrocarbons into hexane, extract cleanup by using solid-phase extraction, and gas chromatography-mass spectrometric analysis using deuterated internal standards. Polyaromatic hydrocarbons were thermally desorbed from soils and sediments without pretreatment in another investigation [61]. 

Langenfeld et al. [48] also compared supercritical monochlorofluoromethane, nitrogen dioxide and carbon dioxide for the extraction of polyaromatic hydrocarbons from sediments. Monochlorodifluoromethane provided the highest recoveries. 

Lopez-Avila et al. [59] have described a microwave assisted extraction procedure for the separation of polyaromatic hydrocarbons from sediments. Tan [71] described a rapid sample preparation technique for analysing polyaromatic hydrocarbons in sediments. Polyaromatic hydrocarbons are removed from the sediment by ultrasonic extraction and isolated by solvent partition and silica gel column chromatography. The sulphur removal step is combined into the ultrasonic extraction procedure. Identification of polyaromatic hydrocarbon is carried out by gas chromatography alone and in conjunction with mass spectrometry. Quantitative determination is achieved by addition of known amounts of standard compounds using flame ionization and multiple ion detectors. 

Lagenfeld et al. [116] studied the effect of temperature and pressure on the supercritical fluid extraction of polychlorobiphenyls and polyaromatic hydrocarbons from soil. At 50°C raising the pressure from 356 to 650atm had no effect on recovery of polychlorobiphenyls. A temperature of 200°C was necessary for effective extraction. 

Table 1. Percent Removal of Polyaromatic Hydrocarbons from Stainless Steel, Copper Sheet, Epoxy Board, and Cast Magnesium using Supercritical CO2...

Furthermore, these results, together with the ease of elution of many tetra- and pentacyclic polyaromatic hydrocarbons from /u.-Porasil columns, as illustrated in Figure 5, confirm the potential of the published HPLC method for petroleum-derived products (4,5,6) where large numbers of bitumen samples are involved. 

Carbopack F, C, or B traps have been used for the enrichment of polyaromatic hydrocarbons from water samples [37 ]. The water to be analyzed is forced through the trap which is finally extracted with toluene. Recoveries higher than 86% were reported for compounds ranging from acenaphtylene to benzo g, h, i perylene. 

Levasseur, G., H. Hutchings, J. Filion, and M.J. Kaiserman Little cigars, big concerns 61st Tobacco Science Research Conference, Program Booklet and Abstracts, Vol. 61, Paper No. 18, 2007, pp. 25-26. Levins, R.J. Isolation of polyaromatic hydrocarbons from whole smoke condensate A simple two-step procedure Chromatagraphia 11 (1978) 736. 

The extraction of polyaromatic hydrocarbons from soil and urban particulates by superheated water was reported in 1994 [17]. Extraction of compounds up to ben-zo[a]pyrene was virtually complete in 15 min at 250°C, with a flow rate of 1 ml mim and a sample of 0.5 g. Good but less complete results were obtained when extracting urban air particulates. The pressure did not influence the extraction behavior, provided it was sufficient to maintain water as a Hquid. The extraction of polychlorinated biphenyls from soil and a river sediment was also found to be complete in 15 min at 250°C [18]. Work with a wider range of compounds showed that extraction was class selective [6, 19], with phenols and Hghter aromatics being extracted at 50 to 150°C, polyaromatic hydrocarbons and lighter ahphatics at 250 to 300°C, but the heavier ahphatics only removed by steam at 250 to 300°C. This selectivity has been compared to other extraction methods [20]. The extraction of agrochemicals from soil has also been studied [6]. 

Fernandez and Bayona [618] developed a method for the fiactionation of polyaromatic hydrocarbons from dichloromethane extracts of air particulates and marine sediment. The resulting fractions were quantitated by GC/MS. A silica column I = 254 nm or 254 nm, ex 390 nm, em) generated the following fractions PCB, PAH, N02-PAH/2°-amine-PAH, keto-PAH, keto-PAH/quinones, quinones, 3°-amine-PAH, and 3°-amine-PAH/hydroxy-PAH. The separation required a 70-min 100/00/100 hexane/dichloromethane gradient. Levels of 47 compounds were monitored, typically well below the pg/g range. 

Supercritical CO2 has also beea tested as a solveat for the removal of organic contaminants from sod. At 60°C and 41.4 MPa (6,000 psi), more than 95% of contaminants, such as diesel fuel and polychlotinated biphenyls (PCBs), may be removed from sod samples (77). Supercritical CO2 can also extract from sod the foUowiag hydrocarbons, polyaromatic hydrocarbons, chlotinated hydrocarbons, phenols, chlotinated phenols, and many pesticides (qv) and herbicides (qv). Sometimes a cosolvent is required for extracting the more polar contaminants (78). 

Chnng WK, GM King (2001) Isolation, characterization, and polyaromatic hydrocarbon potential of aerobic bacteria from marine macrofainal burrow sediments and description of Lutibacterium anuloederans gen. nov., sp. nov., and Cycloclasticus spirillensis sp. nov. Appl Environ Microbiol 67 5585-5592. 

The TLC plates prepared in a similar maimer may be used to separate monoar-omatie hydrocarbon fractions with Rj values in the range 0.29 to 0.78 from polyaromatic hydrocarbon fractions (Rj = 0.06 to 0.29) [84]. 

From the above it can be concluded that the risk for lung cancer induction from chronic indoor exposure to Rn-d is unlikely to be higher than 1.10 4/mSv. in order to understand the magnitude of this risk it has to be emphasized that man can be exposed to a multitude of different hazardous materials in the indoor atmosphere besides Rn-d, such as formaldehyde, nitrogen dioxide, carbon monoxide, nitrosamines, polyaromatic hydrocarbons, volatile organic compounds, asbestos and pesticides (Gammage and Kaye, 1985). 

Much of the study of ECL reactions has centered on two areas electron transfer reactions between certain transition metal complexes, and radical ion-annihilation reactions between polyaromatic hydrocarbons. ECL also encompasses the electrochemical generation of conventional chemiluminescence (CL) reactions, such as the electrochemical oxidation of luminol. Cathodic luminescence from oxide-covered valve metal electrodes is also termed ECL in the literature, and has found applications in analytical chemistry. Hence this type of ECL will also be covered here. 

Boeda et al. (1996) identified bitumen on a flint scraper and a Levallois flake, discovered in Mousterian levels (about 40 000 BP) at the site of Umm el Tlel in Syria. The occurrence of polyaromatic hydrocarbons such as fluoranthene, pyrene, phenanthrenes and chrysenes suggested that the raw bitumen had been subjected to high temperature. The distribution of the sterane and terpane biomarkers in the bitumen did not correspond to the well-known bitumen occurrences in these areas. In other studies of bitumen associated with a wide variety of artefacts of later date, especially from the 6th Millennium BC onwards, molecular and isotopic methods have proved successful in recognizing different sources of bitumen enabling trade routes to be determined through time (Connan et al., 1992 Connan and Deschesne, 1996 Connan, 1999 Harrell and Lewan, 2002). 

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