Polynuclear aromatic hydrocarbons PAHs

The fused 3+ ring aromatics in petroleum include both cata- and peri-condensed stmctures (see Table 4, Fig. 8). The cata-condensed species are those stmctures where only one face is shared between rings, the peri-condensed molecules are those that share more than one face. The fused ring aromatics form the class of compounds known as polynuclear aromatic hydrocarbons (PAH) which includes a number of recognized carcinogens in the 4+ ring family (33). Because of the potential health and environmental impact of PAH, these compounds have been studied extensively in petroleum. 

Aerobic, Anaerobic, and Combined Systems. The vast majority of in situ bioremediations ate conducted under aerobic conditions because most organics can be degraded aerobically and more rapidly than under anaerobic conditions. Some synthetic chemicals are highly resistant to aerobic biodegradation, such as highly oxidized, chlorinated hydrocarbons and polynuclear aromatic hydrocarbons (PAHs). Examples of such compounds are tetrachloroethylene, TCE, benzo(a)pyrene [50-32-8] PCBs, and pesticides. 

Benzene monoxide-oxepin and its sulfur analog are treated elsewhere (Chapter 5.1.7) (67AG(E)385). However, we point out here that electron-withdrawing substituents often favor the benzene oxide tautomer. The first study on oxides of the environmentally hazardous polychloro- and polybromo-biphenyls shows that they exist mainly in the benzene oxide form (81JOC3721). Oxides of polynuclear aromatic hydrocarbons (PAH) also exist mainly in the fused-ring oxirane form. 

Standardization. Standardization in analytical chemistry, in which standards are used to relate the instrument signal to compound concentration, is the critical function for determining the relative concentrations of species In a wide variety of matrices. Environmental Standard Reference Materials (SRM s) have been developed for various polynuclear aromatic hydrocarbons (PAH s). Information on SRM s can be obtained from the Office of Standard Reference Materials, National Bureau of Standards, Gaithersburg, MD 20899. Summarized in Table VII, these SRM s range from "pure compounds" in aqueous and organic solvents to "natural" matrices such as shale oil and urban and diesel particulate materials. 

The theory and development of a solvent-extraction scheme for polynuclear aromatic hydrocarbons (PAHs) is described. The use of y-cyclodextrin (CDx) as an aqueous phase modifier makes this scheme unique since it allows for the extraction of PAHs from ether to the aqueous phase. Generally, the extraction of PAHS into water is not feasible due to the low solubility of these compounds in aqueous media. Water-soluble cyclodextrins, which act as hosts in the formation of inclusion complexes, promote this type of extraction by partitioning PAHs into the aqueous phase through the formation of complexes. The stereoselective nature of CDx inclusion-complex formation enhances the separation of different sized PAH molecules present in a mixture. For example, perylene is extracted into the aqueous phase from an organic phase anthracene-perylene mixture in the presence of CDx modifier. Extraction results for a variety of PAHs are presented, and the potential of this method for separation of more complex mixtures is discussed. 

Wilson SS, KC Jones (1993) Bioremediation of soil contaminated with polynuclear aromatic hydrocarbons PAHs, a review. Environ Pollut 81 229-249. 

In LIF detection systems, excitation power may be increased up to six orders of magnitude compared to CF detection. Most LC-LIF detection concerns under-ivatised polynuclear aromatic hydrocarbons (PAHs) and fluorescing dyes (e.g. polymethines). Because only a limited number of analytes possess native fluorescence, derivatisation of the analyte before detection is normally required in trace analysis of organic solutes by means of LIF detection. LIF detection in HPLC was reviewed... 

Polycyclic (also called polynuclear) aromatic hydrocarbons (PAHs) are composed of multiple rings connected by shared carbon atoms (i.e., separate rings are combined by sharing two carbon atoms). All these compounds are pure hydrocarbons except for the two benzo-fluoranthenes, polychlorinated biphenyls (PCBs), and 2-chloronaphthalene. Moore and Ramamoorthy110 review the behavior of PAHs in natural waters. 

Polynuclear Aromatic Hydrocarbons (PAHs) and Related Aromatic Hydrocarbons... 

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