Evaluation of coal-related model compounds using tandem mass spectrometry

Gas chromatography/mass spectrometry (GC/MS) is a routine and basic instrumental method for the analysis of complex coal conversion products in the chemical industry. To further enhance the practical potential of GC/MS in chemical industry, a tandem MS method for the selection of ion pairs applied in monitoring coal conversions was established using GC/quadrupole time-of-flight MS (GC/Q-TOF MS). The corresponding fragmentation pathways were explored and suitable ion pairs were screened.

Fourteen coal-related model compounds (CRMCs) were analyzed using GC/Q-TOF MS with different collision-induced dissociation (CID) energies (5-20 eV). The fragmentation pathways can offer a better understanding of chemical bond breaking, hydrogen transfer, rearrangement reactions and elimination of neutral fragments for CRMCs during the CID process.

The precursor ions of aromatic hydrocarbons without alkyl chains were difficult to fragment with a CID energy of 20 eV. But aromatic hydrocarbons with branched chains were prone to fragment via the loss of alkyl chains and further fragmented through ring-opening reactions. Compared with the C_alk C_ar bond, the C_ar C_ar bond was difficult to fragment due to its high bond dissociation energy. The existence of heteroatoms facilitated fragmentation that was conducive to the screening of ion pairs.

The CID technique of GC/Q-TOF MS will contribute to studies on the organic composition of coals and to building monitoring methods for coal conversions via fragmentation and ion pair selection.