The soluble organic fraction (SOF) of particulate matter from diesel exhaust (from point sources, ambient air, etc.) contains hundreds of organic constituents. Norman-phase high pressure liquid chromatography (HPLC) has been used to separate the SOF into subfractions suitable for subsequent chemical analysis and bioassays. These fractions consist of non-polar(PAH), moderately polar (transition) and highly polar constituents. The non-polar fractions have been well characterized and consist of PAH and aliphatic hydrocarbons. The specific compounds present in the transition and polar fractions are for the most part unknown. This analytical information has been difficult to obtain since these compounds are highly labile, polar, of low volatility and in very low concentrations when compared to the bulk of material found in the SOF. Mutagenicity tests using the Ames Salmonella typhimurium assay indicate that the transition fraction accounts for most of the mutagenicity when compared to the non-polar (PAH) and polar fractions. A variety of chromatographic and mass spectrometric techniques are described that have been used to determine the composition of the HPLC fractions. More than one hundred species have been identified in the transition fraction of diesel particulate matter using high resolution gas chromatography (HRGC)/high resolution mass spectrometry (HRMS), HPLC and direct-probe high resolution mass spectrometry. It has been found that the transition fraction contains mostly PAH derivatives consisting of hydroxy, ketone, quinone, carboxaldehyde, acid anhydride and dihydroxy derivatives of PAH. Three nitro-PAH species have been tentatively identified and 1-nitropyrene positively identified in the transition fraction. The 1-nitropyrene was found to account for approximately 45% and 30% of the direct-acting mutagenicity observed for the transition fraction and total extract, respectively. The HPLC separation procedure was shown to give better than 95% recovery of the mass and mutagenic activity. The problem of PAH oxidation during the analytical procedures and possible effect on bioassay results are discussed.

The analysis of nitrated polycyllc aromatic hydrocarbons (nltro-PAH) In diesel particulate extracts using a combination of high-performance liquid chromatography, gas chromatography/mass spectrometry, hlgh-resolutlon mass spectrometry, and mass spectrometry/mass spectrometry (MS/MS) techniques Is described. Triple stage quadrupole (TSQ)-MSZMS operated In the constant neutral loss mode Is described for the rapid qualitative screening of nltro-PAH Isomer groups In solvent extracts of diesel particulates. Twenty such Isomer groups of nltro-PAH derivatives were found, many of these groups containing a large number of possible compounds.Mass analyzed Ion kinetic energy spectrometry (MIKES)-MS/MS was found to be much less selective than the TSQ-MS/MS for the analysis of nltro-PAH In unfractionated diesel extracts. HPLC prefractlonatlon was required to remove Interferences In the MIKES analysis. Fused silica capillary GC/MS using on-column Injection was found to be necessary for Indentlfylng specific nltro-PAH Isomers and minimizing decomposition. The highly mutagenic 1-nltropyrene (1-NP) was the only compound found In the nltro(pyrenes and fluoranthenes) Isomer group. The MIKES and TSQ techniques gave comparable results for the quantitation of 1-NP.Organic solvent extracts of diesel exhaust particulates exhibit direct-acting (i.e., activation by mammalian tissue homogenate is not required) mutagenicity (1-5) using the Ames assay (6). High-performance liquid chromatography (HPLC) (1,2,4,5), thin-layer chromatography (TLC) (7,8), and liquid chromatography (9) have been used to fractionate diesel particulate extracts for subsequent mutagenicity testing.

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