Determination of three previously unidentified polycyclic aromatic hydrocarbons of molecular mass 302 Da in particulate Standard Reference Materials (SRMs) and combustion-related samples

Polycyclic aromatic hydrocarbons (PAHs) of molecular mass (MM) 302 Da comprise numerous structural isomers that are of high concern for human health. Because of their multiplicity, low abundance in the environment, and limited availability of authentic standards, their occurrence, composition, and environmental health risk remain not well characterized. Here we extend the characterization of MM 302 Da PAH isomers in combustion-related particulate matter with the addition of four newly synthesized and previously unidentified MM 302 Da isomers: dibenzo[a,l]fluoranthene (DBalF), dibenzo[b,l]fluoranthene (DBblF), dibenzo[a,j]fluoranthene (DBajF), and naphtho[2,1-j]fluoranthene (N21jF). Using a coupled high-performance liquid chromatography/gas chromatography-mass spectrometric system with a 50% phenyl methylpolysiloxane stationary phase, 24 MM 302 Da isomers were annotated in four Standard Reference Materials, SRM 1648a, SRM 1649b, SRM 1650b, and SRM 2975, and in four combustion-related particulate matter samples consisting of two traffic-impacted filters and two laboratory-generated combustion samples. Three of the four previously unidentified compounds, DBalF, DBajF, and N21jF, were chromatographically resolved and quantified for the first time in these samples. Quantitative analysis of nine MM 302 Da PAHs (∑MM302Da) showed that these compounds accounted for roughly 0.66-4.1% of the total mass for 50 PAHs. The previously unidentified isomers were recurring but generally minor contributors to the ∑MM302Da burden, with N21jF representing 8-14%, DBalF typically 6-10% (but 23% in SRM 2975), and DBajF varying between 1 and 5%. These results demonstrate both the ubiquity and compositional variability of MM 302 Da PAHs in combustion-derived particulate matter and provide new reference data for analytical investigations of MM 302 Da PAHs.