Nitroaromatic compounds, determination

A comparison of active (using pumps) and passive (relying on diffusion) sampling techniques for the determination of nitrobenzene, benzene and aniline in air was mentioned in Section IV.A77. Several LLE methods for nitroaromatic compounds dissolved in water were evaluated. High recoveries were achieved with discontinuous or continuous extraction with dichloromethane, adsorption on a 1 1 1 mixture of Amberlite XAD-2, -4 and -8 resins and elution with dichloromethane445. 

A sensitive ELISA procedure was developed for the determination of TNT (221) and other nitroaromatic compounds. TNT can be detected within the range of 0.02-20 ng/L in water samples462. A simplified immunofiltration prepacked portable device for field screening tests of TNT in water and soil was also developed. A quantitative color response to concentrations of TNT in the range 1-30 ng/L in water and 50-1000 pg/g in soil was demonstrated463. 

A. L. Lafleur and K. M. Mills, Trace level determination of selected nitroaromatic compounds by gas chromatography with pyrolysis/chemiluminescent detection. Analytical Chemistry, 1981,53, 1202-1205. 

Shafer KH. 1982. Determination of nitroaromatic compounds and isophorone in industrial and municipal waste waters. U.S. EPA, Off Res Dev, 1-71. 

By treating styrylated PCTFE with concentrated nitric and sulfuric acids, the corresponding nitrated polymer was obtained (Equation 10). In accordance with the IR spectrum of the resulting polymer (Figure 8), bands at 1529 and 1350 cm-1 indicated the nitro group and a band at 856 cm- confirmed the presence of the nitroaromatic compound. However, the extent of nitration was not determined. 

Figure 11 illustrates the parameter space defined by the equilateral triangle. The initial pressure and conditions for the 3 vertices of the pressure gradient/ temperature triangle were determined arbitrarily from the critical conditions of the supercritical fluid (carbon dioxide), the retention characteristics of nitroaromatic compounds, and the following criteria (i) the first analyte should not co-elute with the sample solvent and (ii) the retention factor of the last analyte should not exceed 30. 

Godjehann et al. [199] have applied on-line high performance liquid chromatography coupled to proton NMR to the determination of nitroaromatic compounds in ammunition plant ground waters. 

R.L. Lopez de Compadre et al., LUMO energies and hydrophobicity as determinants of mutagenicity by nitroaromatic compounds in Salmonella typhimurium. Environ. Mol. Mutagen. 15, 44-55 (1990). 

Accordingly, we recently undertook the determination, by means of homodesmic reactions, of the gas and solid phase AHf of six energetic nitroaromatic compounds for which the experimental AHf(solid) are ambiguous, i.e. two or more values differ by at least 6 kcal/mole [64]. Nitroaromatics should be particularly well suited for modeling by means of homodesmic reactions, since all of the participants in these can have the... 

Electrode surface activation can be improved simply by electrochemical pretreatment. Determination of nitroaromatic compounds in water and soil spiked samples have been reported at electrochemically activated carbon-fiber microelectrodes. No interference was found from compounds such as hydrazine, phenolic compounds, carbamates, triazines or surfactants. The detection limit obtained can be approximately 0.03 iigml-1 for all the nitroaromatic compounds (Agui et al. 2005). Chen and coworkers reported an effective field-deployable tool for detecting nitroaromatic compounds with an electrochemically pre-anodized screen-printed carbon electrode (SPE) (Chen et al. 2006). 

Hrapovic, S., Majid, E., Liu, Y., Male, K. and Luong, J. H. T. (2006), Metallic nanoparticle-carbon nanotube composites for electrochemical determination of explosive nitroaromatic compounds. Anal. Chem., 78(15) 5504-5512. 

For each analyte, a primary standard of 1.00 mg/mL of nitroaromatic compound in absolute ethanol was used to make a series of diluted standards in PBS-Tween buffer with concentrations ranging from 10,000 ng/mL to 0.1 ng/mL. An antisera solution of appropriate dilution (as determined from Table I) for the particular coating antigen to be used was prepared in PBS-Tween buffer. Samples of each nitroaromatic standard (1 part) were diluted 1/10 with antisera solution (9 parts)... 

Conclusions. The ELISA method may be a promising tool for analysis of several of the nitroaromatic compounds found at NPL hazardous waste sites. Detection of 2,4-dinitrotoluene, 1,3,5-trinitrobenzene, 2,4-dinitrophenol, and 2,4,6-trinitrotoluene at a lower limit of 1 ng/mL under the conditions of this ELISA suggest that direct detection of 10 ng/mL of these nitroaromatics may be accomplished in environmental samples without sample concentration. Investigations are underway to analyze soil and water samples to determine what, if any, matrix effects there will be in these ELISAs. 

A variety of porous materials can be used for analytical applications. For instance, layer-by-layer hlms assembled by alternate adsorption of mesoporous silica and poly(diallyldimethylammonium chloride) onto glassy carbon electrode can be used for highly sensitive determination of ultratrace nitroaromatic compounds in aqueous solution (Shi et al., 2007). 

Emmrich M, Kaiser M, Rueden H, et al. 1993. Determination of RDX, 2,4,6-trinitrotoluene and other nitroaromatic compounds by high-performance liquid chromatography with photoiodide-array detection. J Chromatogr 645 (1) 89-94. 

Only a few studies have reported the fate of the cyclic nitramine compounds RDX or HMX in sediment matrices. Therefore, further research is needed to determine sorption-desorption dynamics and transformation rates of these compounds in different sediment types and exposure conditions. Unlike exposures to sediments spiked with nitroaromatic compounds, exposure of benthic invertebrates to sediments spiked with RDX and HMX did not elicit lethal toxicity, even at exceedingly high concentrations, and therefore are likely to pose minimal risk to benthic invertebrates at contaminated sites. 

The nitroreductase reactions of NQOl have been studied more thoroughly [29,38,65,66]. Rat NQOl contains FAD with the standard (two-electron reduction) potential at pH 7.0, E°7, of-0.159 V [67], The ability of NQOl to perform two-electron transfer is most probably determined by the instability of its anionic FAD semiqui-none, since the E 7 of FAD/FAD and FAD/FADH- couples are equal to -0.200 V and -0.118 V, respectively [67], The majority of nitroaromatic compounds including TNT are very slow NQOl substrates (kcJKm = 102—104 M 1s 1, kcat = 0.1—1.0 s ), with the exception of TNBO, tetryl, and pentryl, whose reactivities are intermediate (kcJKm > 105 M s kcat > 10 s ). Possibly, NQOl reduces TNT to NHOH-DNTs, which is further reduced to dihydroxylamino-NT at a similar rate. NQOl performs reductive N-denitration of tetryl and pentryl (Equation 9.6) with the formation of picramides, other unidentified products, and 02-, which points to the involvement of single-electron transfer steps [29,66], The relationship between the reactivity of nitroaromatics toward NQOl and their reduction potential is absent the structural parameters determining their selectivity are unclear. 

C. Keuchel, L. Weil, R. Niessner, Enzyme-linked Immunosorbent Assay for the Determination of 2,4,6-Trinitrotoluene and Related Nitroaromatic Compounds , Anal Sci., 8, 9-12 (1992). 

This article has described the results of our studies which were undertaken to determine what type of chemical components in the extracts of diesel exhaust particulate account for their direct-acting mutagenicity in the Salmonella assay. These findings, along with those of other investigators, have demonstrated that this activity can be ascribed to a variety of nitroaromatic compounds, principally, the nitrated derivatives of polycyclic aromatic hydrocarbons. We have also studied the way in which mammalian enzyme activity can affect the mutagenic properties of these compounds. There are clearly future research needs in both of these areas. 

In summary, the use of electrochemistry allows (a) determining the type of o-complexes which are present in the solution (number of waves, peak potential wave) and their relative amounts (intensity of peak wave), (b) establishing the oxidative conversion of the o-complexes into re-aromatized nitroaromatic compounds by observing the reduction in the re-aromatized products, and (c) achieving the final substitution products by performing exhaustive electrolysis of solutions of o-complexes at a precise value of applied potential. 

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