Analysis of nitrated polycyclic aromatic hydrocarbons

Many nitrated polycyclic aromatic hydrocarbons (NPAH) that are present in low concentrations in the environment and in emission sources have been shown to be mutagenic and/or carcinogenic. This paper reviews the current methods of analysis of these compounds with the emphasis on NPAH measurements in ambient particulate matter samples.     

Analysis of nitrated polycyclic aromatic hydrocarbons by liquid chromatography with fluorescence and mass spectrometry detection: air particulate matter, soot, and reaction product studies

Polycyclic aromatic hydrocarbons (PAH) and their nitrated derivatives (nitro-PAH) are environmental pollutants which pose a threat to human health even at low concentration levels. In this study, efficient analytical methods for the analysis of nitro-PAH and PAH (extraction, clean-up, chromatographic separation, and spectrometric detection) have been developed, characterized, and applied to aerosol samples. The separation and quantification of 12 nitro-PAH was carried out by reversed-phase high performance liquid chromatography (HPLC), on-line reduction, and fluorescence detection. The detection limits were in the range of 0.03–0.5 g L^–1 (6–100 pg in the investigated sample aliquots), and the recovery rates from soot samples were 70–90%. Nitro-PAH and PAH concentrations have been determined for different types of soot and for urban, rural, and alpine fine air particulate matter (PM2.5). For the first time, trace amounts of nitro-PAH have been detected in a high-alpine clean air environment. The on-line reduction and fluorescence technique has been complemented by atmospheric pressure chemical ionization time-of-flight mass spectrometry (APCI-TOF-MS). The MS detection allowed the analysis of partially nitrated and oxygenated PAH in laboratory studies of the heterogeneous reaction of PAH on soot and glass fiber substrates with gaseous nitrogen oxides and ozone. It led to the tentative identification of a previously unknown nitrated derivative of the particularly toxic PAH benzo[a]pyrene (BaP-nitroquinone), and provides the first experimental evidence that PAH-nitroquinones can be formed by reaction of PAH with atmospheric photooxidants.     

Determination of nitrated polycyclic hydrocarbons in aerosols using capillary gas chromatography combined with different electron capture detection methods

A method is described which allows the determination of subnanogram concentrations of mono- and dinitrated polyaromatic hydrocarbons with two to four ring systems in aerosol samples. High performance liquid chromatography is used to separate the nitro compounds from other classes of substances. Carbozoles elute in the same fraction. Both electron capture detection and negative ion chemical ionization mass spectrometry combined with capillary gas chromatography are used for quantification. Use of these two methods leads to a considerable improvement of selectivity and sensitivity for nitrated compounds. In contrast to the situation with a nitrogen-sensitive detector, carbazoles do not interfere and detection limits in the order of 10–200 pg/m³ are possible. The applicability of the method is critically discussed. Determination of nitrated polyaromatic hydrocarbons in aerosol samples from an aluminum smelter serves as an example.