Improved GC/MS methods for measuring hourly PAH and nitro-PAH concentrations in urban particulate matter

This study presents two methods for the quantification of nitro-substituted and parent polycyclic aromatic hydrocarbons (NPAH and PAH, respectively), respectively, utilizing large volume injection gas chromatography/mass spectrometry (GC/MS). Both methods (PAH and NPAH, respectively) employed a programmed temperature vaporization injector (PTV) in solvent vent mode, optimized using standard solutions. For the PAH method, the precision of the PTV was comparable to hot splitless injection for exhibiting a percent relative standard deviation (%RSD) consistently below 8% for 100 pg injections. Compound %RSDs for the NPAH method were consistently below 5% using the PTV. Microgram quantities (30-500 μg) of particulate matter Standard Reference Materials (SRM 1649 and 1650, National Institutes of Standards and Technology) were analyzed to simulate PAH and NPAH quantification on small aerosol mass loadings. The method detection limits from this study suggest PAHs and NPAHs can be easily quantified using low-volume samplers (>5 Lpm) on hourly timescales. In addition, this technique enabled the quantification of 12-h NPAH size distributions in the Baltimore, MD, atmosphere.