Fragmentation pathways of some benzothiophene radical cations formed by atmospheric pressure chemical ionisation

Abstract

Polycyclic aromatic sulfur-containing compounds (PASHs) are commonly found in fossil fuels and are of considerable importance in environmental studies. This work presents detailed studies on the fragmentation patterns of radical cations formed from four representative PASHs, benzo[b]thiophene, dibenzothiophene, 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene, using tandem atmospheric pressure chemical ionization mass spectrometry (APCI-MS/MS). Understanding these fragmentation patterns can be a useful aid in the analysis of PASHs employing APCI or electron ionization (EI-MS/MS), either alone or in conjunction with liquid or gas chromatography.

Characterization of aromatic organosulfur model compounds relevant to fossil fuels by using atmospheric pressure chemical ionization with CS2and high‐resolution tandem mass spectrometry

“…The sulfur‐containing neutral molecules that were lost during fragmentation are highlighted in red in Tables , including S (32 Da), HS • (33 Da), H 2 S (34 Da), CS (44 Da), and • CHS (45 Da). In agreement with these results, molecular ions of various aromatic sulfur compounds have been reported to undergo losses of S, HS • , H 2 S, CS and • CHS in mass spectrometers . Generally, losses of HS • and H 2 S were found here to be associated with ions containing aliphatic sulfur functionalities while losses of S, CS and • CHS were more common for ions with heteroaromatic sulfur functionalities.…”

Atmospheric pressure chemical ionization Fourier transform ion cyclotron resonance mass spectrometry for complex thiophenic mixture analysis

“…1). These model PASH components (compounds 1-5) yielded largely intact stable [M + H] + protonated ions without source fragmentation, as shown in [34] The protonated species most likely result from proton transfer from protonated solvent molecules within the APCI source where radical cations result from charge transfer from solvent radical cations. [35] The result demonstrates that a variety of PASHs standards were uniformly ionized without fragmentation under APCI-FTICR MS conditions.…”

“…The protonated ions are found at m/z 235, 253, 285, 333 and 336. Both ionized species are known to be produced for PASHs under APCI conditions . The protonated species most likely result from proton transfer from protonated solvent molecules within the APCI source where radical cations result from charge transfer from solvent radical cations .…”

“…Subsequently, four PASH standards were further analyzed by (+)‐APCI‐MS. Molecular ions were readily observed for the investigated species at lower source cone voltages . The APCI studies mentioned above showed the ionization patterns for only low‐mass PASH standards.…”

“…Subsequently, four PASH standards were further analyzed by (+)-APCI-MS. Molecular ions were readily observed for the investigated species at lower source cone voltages. [34] The APCI studies mentioned above showed the ionization patterns for only low-mass PASH standards. Furthermore, the product ions were not uniform among these APCI studies which also mainly focused on model systems or reference materials.…”