Polyaromatic hydrocarbons pyrenes

Figure 5.12 Polyaromatic hydrocarbon species (1) phenanthrene, (2) anthracene, (3) pyrene, (4) benz[o]anthracene, (5) chrysene, (6) naphthacene, (7) benzo[c]phenanthrene, (8) benzo[ghi] fluoranthene, (9) dibenzo[c,g]phenanthrene, (10) benzo[g/ ]perylene, (11) triphenylene, (12) o-terphenyl, (13) m-terphenyl, (14) p-terphenyl, (15) benzo[o]pyrene, (16) tetrabenzonaphthalene, (17) phenanthro[3,4-c]phenanthrene, (18) coronene...

Polyaromatic hydrocarbons Synthetic 10"5-10"7 mol L"1 (anthracene, rubrene, pyrene)... 

Sometimes orthogonal offline SPE steps were used prior to online SPE LC/MS/MS. These preparation steps were used to remove interference and concentrate samples. In an application to measure urinary N7-(benzo[a]pyren-6-yl)guanine (BP-6-N7Gua), a biomarker for exposure to polyaromatic hydrocarbons (PAHs), a two-step offline SPE was first performed using Sep-Pak C8 (Waters, Milford, Massachusetts) and Strata SCX (Phenomenex, Torrance, California) cartridges to obtain high sensitivity (Chen et al. 2005). The extracts were applied to an online reversed phase SPE LC/MS system. The lower limit of detection was 2.5 fmol/mL when 10 mL of urine was used. 

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). 

Fowlie and Bulman [43] have carried out a detailed study of the extraction of anthracene and benzo[tf]pyrene from soil. They carried out a replicated [24] factorial experiment using Soxhlet extraction and Polytron techniques. Soxhlet extraction followed by thin layer chromatography gave higher recoveries of the two polyaromatic hydrocarbons. 

In this study the soil samples were spiked with labelled and unlabelled benzo[<2]pyrene, or anthracene at 5 and 50pg/g soil. The samples were incubated in biometer flasks at 20°C for three and five months for anthracene and benzo[a]pyrene, respectively, allowing degradation to be monitored and the polyaromatic hydrocarbon to interact with the soil matrix. 

Dunn and Stich [78] and Dunn [79] have described a monitoring procedure for polyaromatic hydrocarbons, particularly benzo[a]pyrene in marine sediments. The procedures involve extraction and purification of hydrocarbon fractions from the sediments and determination of compounds by thin layer chromatography and fluorometry, or gas chromatography. In this procedure, the sediment was refluxed with ethanolic potassium hydroxide, then filtered and the filtrate extracted with isooctane. The isooctane extract was cleaned up on a florisil column, then the polyaromatic hydrocarbons were extracted from the isoactive extract with pure dimethyl sulphoxide. The latter phase was contacted with water, then extracted with isooctane to recover polyaromatic hydrocarbons. The overall recovery of polyaromatic hydrocarbons in this extract by fluorescence spectroscopy was 50-70%. 

A1 Planar polyaromatic hydrocarbons (PAHs) Benzo[ ] pyrene 1-Ethynyl pyrene TCDD, PAHs Many PAHs... 

Stationary phases with a high density of bonded alkyl groups can differentiate between two molecules of identical size where one is planar and the other twisted out of plane. This shape selectivity has been described by Sander and Wise [53] for polymeric stationary phases, where in the preparation, water has been added on purpose and trichloro alkyl silanes have been used. The selectivity for the retention of tetrabenzonaphthalene (TEN) and benzo[a]pyrene (BaP) was taken as a measure to differentiate between polymeric and standard RP columns. With standard ( monomeric ) RP columns, the twisted TBN elutes after the planar BaP, which on the other hand is more strongly retarded as TBN on polymeric stationary phases. In these cases the relative retention of TBN/ BaP is smaller than 1, whereas with monomeric phases the value is >1.5. The separation of the standards on three different phases is shown in Figure 2.9. These stationary phases have superior selectivity for the separation of polyaromatic hydrocarbons in environmental analysis. Tanaka et al. [54] introduced the relative retention of triphenylene (planar) and o-terphenyl (twisted), which are more easily available, as tracers for shape selectivity. However, shape selectivity is not restricted to polymeric phases, monomeric ones can also exhibit shape selectivity when a high carbon content is achieved (e.g., with RP30) and silica with a pore diameter >15 nm is used [55]. Also, stationary phases with bonded cholestane moieties can exhibit shape selectivity. 

Many polycyclic aromatic amines and aldehydes are commercially available, but their supply is very limited. Preparation of these starting materials is necessary for studying the (3-lactam formation reaction [93]. Nitro compounds are the precursors for the amines. An important task was to prepare polycyclic aromatic nitro compounds, particularly those of chrysene, phenanthrene, pyrene, and dibenzofluorene in good yield. Nitration of these hydrocarbons with concentrated nitric acid in sulfuric acid is a widely used reaction for this purpose. Our research culminated in facile synthesis of polyaromatic nitro derivative 9 starting from polyaromatic hydrocarbons (PAHs) 8 through the use of bismuth nitrate impregnated with clay (Scheme 1) ([94, 95] for some examples of bismuth nitrate-catalyzed reactions... 

Pairs of polyaromatic hydrocarbons eg benzo(a)pyrene and benzo(e)pyrene [214]... 

Polyaromatic hydrocarbons (naphthalene, fluorene, phen-anthrene, pyrene, benz[a]anthracene Linear polymer coated capillary [poly(N-tert.-butyl acrylamide-co-2-acrylamido-2-methyl-1 -propanesulfonic acid] Acetonitrile-50 mA/Tris buffer, pH 7.3 (30 70) 600 mm x 25 pm i.d. 450 mm effective column length 11... 

Polyaromatic hydrocarbons (naphthalene, fluorene, anthracene, pyrene), acetone... 

Oxidation of phenols, dyes, and polycyclic aromatic hydrocarbons [48,49], decolorization of Kraft bleaching effluents, binding of phenols and aromatic amines with humus [47] Transformation of phenols, aromatic amines, polyaromatic hydrocarbons, and other aromatic compounds, decolorization of Kraft bleaching effluents, treatment of dioxins, pyrene [86-89,114] Improved sludge dewatering [59]... 

The formation of novel membrane-like materials based on LDHs has also been established. These materials are of relevance to separation and membrane technologies. A LiAl-LDH containing myrisate or hexanoate anions, for example, has the ability to partition pyrene from a methanol/water solution containing the polycyclic aromatic [132], No sorption of pyrene was observed for a LiAl(succinate) LDH, however, and this was attributed to a sieving effect of this compound towards the pyrene molecule. The sorption of polyaromatic hydrocarbons, such as pyrene, is important from an environmental perspective. 

The effect of curvature on the aromatic character of polyaromatic hydrocarbons (PAHs) can be studied by comparing planar PAHs and their curved analogues. In order to address this issue a variety of [n](2,7)pyrenophanes (n = 7-10) in which the pyrene (22) moiety is strongly distorted from planarity have been synthesized and studied45. The degree of distortion from planarity and therefore the strain in these systems is controlled by the length and type of the tether that connects the two remote ends (positions 2 and 7) of 22. 

Arsenic, asbestos, benzo(a)pyrene, hK(chloromethyl)ether, chromium, nickel subsulfide, zinc chromate, tobacco, mustard gas, uranium, acrylonitrile, beryllium, cadmium, l,2-dibromo-3-chloropropane, polyaromatic hydrocarbons (PAHs)... 

Arsenic, benzo(a)pyrene, polyaromatic hydrocarbons, tetrachloroethylene... 

These compounds are another example of nonionic, nonpolar compounds. They are found in trace levels in water and result from combustion processes and hydrocarbon spills. They are trace enriched from water by sorption onto CN, C-8, or C-18 and elution with ethyl acetate/toluene. Toluene is added to the ethyl acetate eluent to increase solubility of the polyaromatic hydrocarbons (PAHs) and to enhance elution from the solid phase. The more hydrophobic PAHs, such as pyrene (Fig. 7.11), will recover more efficiently from a more polar reversed phase, such as CN or C-8 due to less strong van der Waals interactions between the analyte and the sorbent. The PAHs may be analyzed by either GC/MS or by HPLC. Soil samples may be processed as in Section 7.10.2 with 90% methanol extraction, followed by dilution with... 

Fig. 4.4.10. Separation of a polyaromatic hydrocarbon mixture on 5 different brands of chemically bonded ODS-silica, the carbon content of the individual materials are given in brackets, a, HC-ODS (8.5%) b, LiChrosorb RP-18 (19.8%) c, Partisil-10 ODS-2 (16%) d, Zorbax ODS (10%) e, pBondapak C,g (10%). Peaks 4, benz[a]anthracene 5, chrysene 6, benzo[e]pyrene 7, benzo b]fluoroanthrene 8, benzo k]fIuoroanthrene 11, benzo[ghi]perylene 12, indeno[l,2,3-c,d]pyrene. Reprinted from Ref. 14 with permission.

Special attention is paid to polyaromatic hydrocarbons, since some of them are carcinogenic. Benzo[o]pyrene is the most typical of such species. Its greatest amounts are formed during engine idling at minimum rpm. 

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