PNA

Outside of carbon monoxide for which the toxicity is already well-known, five types of organic chemical compounds capable of being emitted by vehicles will be the focus of our particular attention these are benzene, 1-3 butadiene, formaldehyde, acetaldehyde and polynuclear aromatic hydrocarbons, PNA, taken as a whole. Among the latter, two, like benzo [a] pyrene, are viewed as carcinogens. Benzene is considered here not as a motor fuel component emitted by evaporation, but because of its presence in exhaust gas (see Figure 5.25). 

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. 

The petroleum oils are of three basic types aromatic, naphthemic, and paraffinic. Aromatic oils contain hazardous materials that require special handling precautions. Naphthenic oil does not contain hazardous levels of polynuclear aromatics (PNAs) and is less hysteretic. Because of these considerations the naphthenic oil is gaining in usage at the expense of more utilized aromatics. Paraffinic oil is only used modestly in tire compounds. The... 

T -nitro aniline (PNA) [100-01-6] ammonia T -phenylenedi-amine gasoline antioxidants, dyes, mbber chemicals... 

EP(D)M is not classified as ha2ardous. It is not considered carcinogenic according to OSHA Ha2ard Communications Standard and lARC Monographs. Commonly used paraffinic extender oils contain less than 0.1 wt % polynuclear aromatics PNAs. 

Figure 3.12 depicts TOP SIMS spectra obtained from ODN and PNA immobilized on silanized silicon wafers. The spectra clearly demonstrate that the masses corresponding to POi and PO3 provide the best correlation of the presence of ODN, enabling their use for precise distinction between ODN and PNA. The CFJ and C2O2FJ peaks seen in the PNA spectra represent trifluoroacetic acid, which was part of the PNA solution. Deprotonated (Cyt-H) and (Thy-H) signals of the bases cytosine and thymine are observed for both immobilized PNA and ODN sequences and can be used to detect the presence of these bases. 

Figure 3.13 shows the thermal stability of immobilized ODN and PNA. The signal for the Thy- and Cyt-bases obtained with temperature-programmed (TP) SIMS starts to decrease at approximately 150 °C for ODN and 200 °C for PNA. This variance is caused by the different strengths of binding between the bases and the sugar-phosphate and peptide backbones, respectively. 

Fig. 3.12. NegativeTOF SIMS spectra obtained from oligodeoxy-nucleotides (ODN) (left) and PNA (right) [3.26].

Peptide Nucleic Acids (PNAs) Are Synthetic Mimics ofDNA and RNA... 

H. Boer and P. van Arkel, Automatic PNA (paraffin-naphthene-aromatic) analyzer for (heavy) naphtha , Chromatographia 4 300-308 (1971). 

Polynuclear aromatics (PNA) do not react in the FCC and tend to remain in coke. Adding hydrogen to the outer ring clusters makes them more crackable and less likely to form coke on the catalyst. 

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