Determination of aromatic sulphur compounds in heavy gas oil by using (low-)flow modulated comprehensive two-dimensional gas chromatography–triple quadrupole mass spectrometry

• A low-flow modulated pressure comprehensive 2D GC–MS/MS method was developed.
• The FM GC × GC–MS/MS method was used for the determination of aromatic S compounds in heavy gas oil.
• The simultaneous full-scan/MRM mode enabled the generation of both untargeted and targeted data.
• Benzothiophene, dibenzothiophene and benzonapthothiophene classes were subjected to semi-quantification.
• No pre-fractionation was performed due to the high method selectivity.

The present research is focused on the development of a flow-modulated comprehensive two-dimensional gas chromatography–triple quadrupole mass spectrometry (FM GC × GC–MS/MS) method for the determination of classes of aromatic organic sulphur compounds (benzothiophenes, dibenzothiophenes, and benzonaphthothiophene) in heavy gas oil (HGO). The MS/MS instrument was used to provide both full-scan and multiple-reaction-monitoring (MRM) data. Linear retention index (LRI) ranges were used to define the MRM windows for each chemical class. Calibration solutions (internal standard: 1-fluoronaphthalene) were prepared by using an HGO sample, depleted of S compounds. Calibration information was also derived for the thiophene class (along with MRM and LRI data), even though such constituents were not present in the HGO. Linearity was satisfactory over the analyzed concentration range (1–100 mg/L); intra-day precision for the lowest calibration point was always below 17%. Accuracy was also satisfactory, with a maximum percentage error of 3.5% (absolute value) found among the S classes subjected to (semi-)quantification. The highest limit of quantification was calculated to be 299 μg/L (for the C1-benzothiophene class), while the lowest was 21 μg/L (for the C4-benzothiophene class).