Polynuclear aromatics, analytical

Finally it is likely that attention will be focused on emissions of polynuclear aromatics (PNA) in diesel fuels. Currently the analytical techniques for these materials in exhaust systems are not very accurate and will need appreciable improvement. In conventional diesel fuels, emissions of PNA thought to be carcinogenic do not exceed however, a few micrograms per km, that is a car will have to be driven for several years and cover at least 100,000 km to emit one gram of benzopyrene for example These already very low levels can be divided by four if deeply hydrotreated diesel fuels are used. 

Troost and Olavesen investigated the application of an internal standardization to the quantitative analysis of polynuclear aromatic hydrocarbons. The following results were obtained for the analysis of the analyte phenanthrene using isotopically labeled phenanthrene as an internal standard... 

Silica gel, per se, is not so frequently used in LC as the reversed phases or the bonded phases, because silica separates substances largely by polar interactions with the silanol groups on the silica surface. In contrast, the reversed and bonded phases separate material largely by interactions with the dispersive components of the solute. As the dispersive character of substances, in general, vary more subtly than does their polar character, the reversed and bonded phases are usually preferred. In addition, silica has a significant solubility in many solvents, particularly aqueous solvents and, thus, silica columns can be less stable than those packed with bonded phases. The analytical procedure can be a little more complex and costly with silica gel columns as, in general, a wider variety of more expensive solvents are required. Reversed and bonded phases utilize blended solvents such as hexane/ethanol, methanol/water or acetonitrile/water mixtures as the mobile phase and, consequently, are considerably more economical. Nevertheless, silica gel has certain areas of application for which it is particularly useful and is very effective for separating polarizable substances such as the polynuclear aromatic hydrocarbons and substances... 

Sulfur Compounds. All crude oils contain sulfur in one of several forms including elemental sulfur, hydrogen sulfide, carbonyl sulfide (COS), and in aliphatic and aromatic compounds. The amount of sulfur-containing compounds increases progressively with an increase in the boiling point of the fraction. A majority of these compounds have one sulfur atom per molecule, but certain aromatic and polynuclear aromatic molecules found in low concentrations in crude oil contain two and even three sulfur atoms. Identification of the individual sulfur compounds in the heavy fractions poses a considerable challenge to the analytical chemist. 

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. 

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... 

The most commonplace substrates in energy-transfer analytical CL methods are aryl oxalates such as to(2,4,6-trichlorophenyl) oxalate (TCPO) and z s(2,4-dinitrophenyl) oxalate (DNPO), which are oxidized with hydrogen peroxide [7, 8], In this process, which is known as the peroxyoxalate-CL (PO-CL) reaction, the fluorophore analyte is a native or derivatized fluorescent organic substance such as a polynuclear aromatic hydrocarbon, dansylamino acid, carboxylic acid, phenothiazine, or catecholamines, for example. The mechanism of the reaction between aryl oxalates and hydrogen peroxide is believed to generate dioxetane-l,2-dione, which may itself decompose to yield an excited-state species. Its interaction with a suitable fluorophore results in energy transfer to the fluorophore, and the subsequent emission can be exploited to develop analytical CL-based determinations. 

Supercritical fluid extraction (EPA 3540, for total recoverable petroleum hydrocarbons EPA 3561 for polynuclear aromatic hydrocarbons) is applicable to the extraction of semivolatile constituents. Supercritical fluid extraction involves heating and pressuring a mobile phase to supercritical conditions (where the solvent has the properties of a gas and a liquid). The supercritical fluid is passed through the soil sample, and the analytes are concentrated on a sorbent or trapped cryogenically. The analytes are eluted with a solvent and analyzed using conventional techniques. Carbon dioxide is the most popular mobile phase. 

In this paper, the supercritical fluid extraction (SFE) of organic compounds from sand spiked with 36 nitroaromatic compounds, 19 haloethers, and 42 organochlorine pesticides, and from a standard reference material certified for 13 polynuclear aromatic hydrocarbons (PAH), dibenzofuran, and pentachlorophenol was examined using a two- and a four-vessel extractor. Although the results achieved by SFE for the sand and the standard reference soil samples were very encouraging, previous data obtained in our laboratory on the standard reference soil and a few other standard reference marine sediments were less favorable. It was therefore decided that an investigation of seven variables for their influence on the analyte recoveries from the standard soil sample would be useful. Two tests were conducted in which these variables were investigated. In Test 1, the seven variables selected were pressure, temperature, moisture content, cell volume, sample size, extraction time, and modifier volume. In Test 2, the seven variables were pressure, temperature, volume of toluene added to the matrix, volume of solvent in the collection vessel,... 

Organic substances that are not volatile are grouped under semivolatiles. The latter class also includes substances of very low volatility such as chlorinated biphenyls and polynuclear aromatics. As far as the GC/MS technique goes, the principle of analysis of the semivolatile organics is not so distinctly different from that of the volatile organics. On the other hand, the method of extraction of analytes from the sample matrices and the sample concentration steps for these semivolatile organic compounds vastly differ from the volatile organics. Such extraction techniques and the sample cleanup methods are discussed more extensively in Chapter 1.5. 

Enzyme immunoassay kits are now available for qualitative field testing or for laboratory screening and semiquantitative analysis of pesticides, herbicides, polychlorinated biphenyls (PCBs), mononuclear and polynuclear aromatic hydrocarbons, pentachlorophenol, nitroorganics, and many other compounds in aqueous and soil samples. Certain analytes may be quantitatively determined as well, with a degree of accuracy comparable to gas chromatography or high performance liquid chromatography determination. The method is rapid and inexpensive. 

There are 14 analytical methods developed by U.S. EPA for measuring common organic pollutants in air. These analytes include aldehydes and ketones, chlorinated pesticides, polynuclear aromatic hydrocarbons, and many volatile organic compounds. These methods may also be applied to analyze other similar substances. All these methods are numbered from TO-1 to TO-14 and based on GC, GC/MS, and HPLC analytical techniques. Method numbers, sampling and analytical techniques, and the types of pollutants are outlined in Table 1, while individual substances are listed in Table 2. 

Similarly, many xenobiotics, such as pesticides, polynuclear aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), plasticizers, phenols, and some other dmg residues, are also toxic even at trace levels present in the earth s ecosystem [5-7], Without analytical techniques capable of detecting them at nanolevels, we assume the absence of these pollutants in the environment, while these notorious pollutants accumulate in our body tissues resulting in various diseases and side effects such as carcinogenesis and failure of many vital body organs including the kidney, liver, and heart [8-11]. Under such situations, it is essential to have analytical techniques that can detect dmgs, pharmaceuticals, and xenobiotics in biological and environmental samples at very low concentrations. 

Finklemann, H., Laub, R.J., Roberts, W.E., and Smith, C.A., Use of mixed phases for enhanced gas chromatographic separation of polycychc aromatic hydrocarbons. II. Phase transition behavior, mass-transfer non-equilibrium, and analytical properties of a mesogen polymer solvent with silicone diluents, in Polynuclear Aromatic Hydrocarbons, Phys. Biol. Chem. 6th Int. Symp., Cooke, M., Ed., Battelle Press, Columbus, OH, 1982, p. 275. 

Analytical Properties Separation of polynuclear aromatic hydrocarbons Reference 24... 

Analytical Properties Separation of polynuclear aromatic hydrocarbons (of the type often encountered in petroleum residue work) by donor-acceptor complex formation Reference 5, 6... 

Analytical Properties Separations via interactions with n-electrons of solutes can be used in both normal and reverse phase for such n-donor systems as polynuclear aromatic hydrocarbons Reference 33... 

Analytical Properties Separates aromatic and polynuclear aromatic hydrocarbons can be used in normal phase mode (commonly using n-heptane or n-heptane + dichloromethane liquid phases) or reverse phase mode (commonly using methanol + water, acetonitrile + water, or phosphate-buffered liquid phases) Reference 45... 

Analytical Properties Separation of aromatic species, including polynuclear aromatic species, by charge transfer interactions Reference 47... 

The Analytical Chemistry Division of PETC is developing the sampling and analytical methodologies for the trace organics. The effort to date has been focused on the problems involved in sampling the hot (ca. 350°F) exhaust gases and on the analysis of the gases for polynuclear aromatic hydrocarbons. ... 

Sonnefeld, W. J., Zoller, W. H. May, W. E. (1983). Dynamic coupled-column liquid chromatographic determination of ambient temperature vapor pressures of polynuclear aromatic hydrocarbons. Analytical Chemistry, 55, 275-80. 

The fluorescence detector is a specific and concentration-sensitive detector. It is based on the emission of photons by electronically excited molecules. Fluorescence is especially observed for analytes with large conjugated ring systems, e.g., polynuclear aromatic hydrocarbons and their derivatives. In order to extend its applicability range, pre-column or post-column derivatization strategies have been developed [9]. 

M. L. Lee, M. V. Novotny, and K. D. Bartle, Analytical Chemistry of Polynuclear Aromatic Hydrocarbons, Academic Press. New York, 1981. 

Pancirov, R. J. and R. A. Brown. 1975. Analytic methods for polynuclear aromatic hydrocarbons in crude oils, heating oils, and marine tissues. In Proceedings of the 1975 Conference on Prevention and Control of Oil Pollution, March 25-27, 1975. San Francisco, CA. American Petroleum Institute Washington, DC., 103-114. 

The first considerations in determining the most appropriate SPE methodology are the structure and polarity of the analytes of interest. Table 7.1 shows a selection of environmentally important compounds as examples for SPE methods development from aqueous solution. The polarity range of environmentally important analytes is broad and stretches from nonpolar compounds, such as polychlorinated biphenyls (PCBs), dioxin, and l,l,l-trichloro-2-2-bis(4-chlorophenyl)ethane (DDT), to moderately nonpolar compounds, such as polynuclear aromatic hydrocarbons (PAHs), to polar compounds such as the herbicides. The most polar compounds are those containing multiple polar functional groups or an ionic functional group, either anionic or cationic. The type of SPE cartridge and elution solvent that are used depends on the polarity of the compound. 

The extraction of polynuclear aromatic hydrocarbons (PAHs) from water may effectively be accomplished with C-18 and a reversed-phase mechanism. The method is straightforward and consists of isolation of the analytes from a 1-L sample, followed by elution with ethyl acetate and with methylene chloride. The combination of solvents is needed for the most hydrophobic of the PAHs. The disk is cleaned with the elution solvents before addition of the sample. 

Weyand EH, Amin S, Sodhi R, et al. 1991c. Effects of methyl substitution on the metabolism and binding of benz[e]acephenanthrylene. In Garriques P, Lamotte M, eds. Polycyclic aromatic compounds. Synthesis, properties, analytical measurements, occurence, and biological effects. Proceedings of the thirteenth international symposium on polynuclear aromatic hydrocarbons. Philadelphia, PA Gordon and Breach. 

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