Interactive tools to assist convenient group-type identification and comparison of low-temperature coal tar using GC × GC–MS
Coal tar is considered a valuable product obtained from coal pyrolysis. An accurate and convenient analytical study on its composition would be of great significance for its further processing and utilization. This work focused on the group-type identification and comparison of low-temperature coal tar by using comprehensive two-dimensional gas chromatography-mass spectrometry (GC × GC–MS). In this work, three low-temperature coal tar samples, diluted in dichloromethane, were analyzed by GC × GC–MS. It was observed that aliphatic hydrocarbons, benzene series, phenolic compounds, benzenediol compounds, naphthol compounds, naphthalene series, anthracene series, indene series and other different types of compounds in coal tar exhibited zonal distribution in the two-dimensional contour plot. The classification of different groups can be achieved by construction of spatial polygons. The classification results showed good reliability confirmed by manually identifying each compound contained in each group. The application of computer language for identifying compounds (CLIC) based on mass fragment characteristics and retention time assisted greatly in the identification of different chemical groups. Five major chemical groups including aliphatics, aromatics, oxygen-containing compounds, nitrogen-containing compounds and sulfur-containing compounds were retrieved from the two-dimensional contour plot by automated pattern recognition using CLIC expressions. The relative content of different chemical groups between a series of contour plots can be conveniently compared by comprehensive implementation of CLIC expressions and an interactive feature template matching function.