Unprecedented Insights into the Chemical Complexity of Coal Tar from Comprehensive Two-Dimensional Gas Chromatography Mass Spectrometry and Direct Infusion Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Coal tar and its distilled products (e.g., creosote) are commonly applied wood preservatives and asphalt sealants that have been identified as significant sources of polycyclic aromatic hydrocarbons (PAHs) to the environment. Despite predictions that coal tar is composed of hundreds of compounds, few studies have ventured beyond measuring select PAHs with gas chromatographymass spectrometry (GC-MS). Expanding the target analyte list will improve our capacity to gauge the inputs and impacts of organic compounds released from coal tar and its products into the environment. Employing a complementary approach with comprehensive two-dimensional gas chromatography (GC X GC) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), we analyzed residues suspected to be coal tar or creosote collected from beaches along coastal Texas in 2014. Over 3000 peaks were observed by GC x GC (compared to the 250 peaks found by our GC-MS analysis) in the whole extract of the samples. To remove PAHs and focus on less abundant compounds, we used silica-gel chromatography to isolate eight fractions. Analysis of each silica-gel fraction by GC X GC led to the tentative identification of over 6600 peaks, including numerous nitrogen-containing heterocycles. Focusing on compounds not amenable to gas chromatography, atmospheric pressure photoionization (APPI) FT-ICR MS revealed 14 000 mass spectral peaks between 150 and 900 Da, mainly aromatics and heterocycles with up to two nitrogen or three oxygen atoms per molecule. On the basis of a comparison of the FT-ICR MS data to the Boduszynski continuum, we confirmed that these samples were residues of a whole coal tar and not a distillate cut point such as creosote.