Identification of organic components in coal tar by pressurized fluid extraction in conjunction with comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry

Abstract

Coal tar (CT) is an important source of high-value chemicals (phenols and arenes), and accurate analysis of CT is crucial for extracting these chemicals. In this study, pressurized fluid extraction (PFE) was used to simplify the analysis of medium- and low-temperature coal tar (M/LTCT). The extract was analyzed with comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC × GC/TOF-MS) to identify the M/LTCT organic components (M/LTCTOC). The extraction solvents were effectively screened by examining the composition and structure of the extracts, with acetonitrile extracts containing the highest abundance of high-value compounds such as phenols and arenes. Furthermore, the detected compounds in the M/LTCTOC were accurately identified by GC × GC/TOF-MS according to the separation mechanism of the two columns and the “tile effect” of homologous compounds. A total of 736 organic constituents were identified, including alkanes, alkenes, cycloalkanes, arenes, phenols, and other heteroatom-containing organic compounds. Biomarkers were also identified and analyzed in detail. Compared with the conventional GC/MS analysis of complex mixtures, GC × GC/TOF-MS can effectively enhance the separation of organic compounds, avoid co-elution of compounds, reveal more structural and compositional details of M/LTCTOCs, and ensure the efficient separation and identification of high-value compounds.