Determination of 252-302 Da and tentative identification of 316-376 Da polycyclic aromatic hydrocarbons in Standard Reference Materials 1649a Urban Dust and 1650b and 2975 Diesel Particulate Matter by accelerated solvent extraction-HPLC-GC-MS.

We have assessed and compared the extraction recoveries of polycyclic aromatic hydrocarbons (PAHs) with molecular weights of 252, 276, 278, 300 and 302 from diesel particulate matter (PM) and urban air particles using ultrasonically assisted extraction and accelerated solvent extraction methods, and evaluated the effects of sample and treatment parameters. The results show that accelerated solvent extraction can extract PAHs more efficiently from diesel PM than ultrasonically assisted extraction. They also show that PAHs are more difficult to extract from diesel PM than from urban air particles. Using toluene and maximum instrumental settings (200 degrees C, 3,000 psi and five extraction cycles) with 30-min static extraction times > 85% of the analytes were estimated to be extracted from the diesel particles, but four extraction cycles with just 5-min static extraction times under these conditions seem to be sufficient to extract > 95% of the analytes from the urban air particles. The accelerated solvent extraction method was validated using the Standard Reference Materials (SRM) 1649a, Urban Dust, and SRM 2975 and SRM 1650a, Diesel Particulate Matter, from the US National Institute of Standards and Technology (NIST). PAH concentrations determined by on-line high-performance liquid chromatography-gas chromatography-mass spectrometry (HPLC-GC-MS) following the developed accelerated solvent extraction method were generally higher than the certified and reference NIST values and concentrations reported in the literature (e.g. the estimated concentration of benzo[a]pyrene in SRM 2975 was 15-fold higher than the NIST-certified value), probably because the extraction recoveries were higher than in previous studies. The developed accelerated solvent extraction method was used to analyse high molecular (HMW) weight PAHs (MW > 302) in the investigated SRMs, and more than 170 (SRM 1649a), 80 (SRM 1650b) and 60 (SRM 2975) potential high molecular weight PAHs were tentatively identified in them, with molecular weights (depending on the SRM sample analysed) of 316, 326, 328, 340, 342, 350, 352, 366, 374 and 376. This is, to our knowledge, the first study to tentatively report PAHs with molecular weights of 316, 326, 328, 342, 350, 352, 366 and 376 in diesel particulate matter. GC-MS chromatograms obtained in selected ion monitoring mode (extracted ions for the abovementioned m/z) and full-scan mass spectra of tentatively identified high molecular weight PAHs are shown in the Electronic supplementary material.