The Analysis of Nitro Polycyclic Aromatic Hydrocarbons in Diesel Exhaust and Urban Airborne Particulate Samples

Abstract

<p>Analytical methodology has been developed for the determination of nitro polycyclic aromatic hydrocarbons (nitro-PAHs), polycyclic aromatic hydrocarbons (PAHs) and other PAH derivatives in diesel exhaust and urban airborne particulate samples. Samples were Soxhlet extracted with methylene chloride for twenty-four hours and the organic extract filtered to remove particulate matter. This extract was taken through a three stage clean-up procedure. Very polar materials were initially removed using a silica Sep-Pak. The aromatic compounds were than separated from the aliphatic substances by Sephadex LH-20 chromatography. Normal phase semi-preparative high performance liquid chromatography was used for the final fractionation of the aromatic compounds. Three fractions, containing PAHs (Fraction A), nitro-PAHs (Fraction B) and dinitro-PAHs (Fraction C), were collected for further analysis. Two diesel exhaust (Oldsmobile and Peugeot) and four airborne particulate (Toronto and Hamilton, Ontario) samples were taken through this procedure.</p> <p>Capillary column gas chromatography (GC) with flame ionization and nitrogen-selective detection was used for the detection and quantitation of nitro-PAHs. Confirmation of the identity of nitro-PAHs was done by capillary column GC-MS in the selected-ion-monitoring mode and other compounds were identified by capillary column GC-MS in the full scanning mode of operation.</p> <p>Nitro-PAHs including 1-nitropyrene, nitro(phenanthrenes/anthracenes), methylnitro(phenanthrenes/anthracenes), nitrobenzo[a]fluorene and 6-nitrobenzo[a]pyrene were confirmed and quantitated in the samples using 1-nitronaphthalene as an internal standard. PAHs, found in Fraction A, and oxygenated-PAHs (e.g., ketone- and quinonederivatives of PAHs) found in Fractions B and C were tentatively identified and their levels estimated.</p>