Isolation and characterization of sulfur-containing compounds by positive-ion electrospray ionization and online HPLC/Atmospheric pressure chemical ionization coupled to Orbitrap mass spectrometry

• Published in: Fuel (Guildford) Vol. 289; p. 119783
• Main Authors: Santos de Freitas, Carla, Valencia-Dávila, Jeferson A., Lopes Pereira, Rosana Cardoso, Torres Abrantes, Luiza, Kato, Lucília, Gontijo Vaz, Boniek
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-04-2021; Elsevier BV
• Subjects: Asphaltenes; Atmospheric pressure chemical ionization; Cartridges; Cation exchange; Cation exchanging; Cations; Copper; Crude oil; Dibenzothiophene; Electrospray ionization; Fractionation; Gas oil; Heavy petroleum; High performance liquid chromatography; Imprinted polymers; Ionization; Ions; LC-MS; Ligand exchange chromatography; Liquid chromatography; Mass spectrometry; Mass spectroscopy; Metal ions; Methylation; Polymers; Scientific imaging; Silica; Silicon dioxide; Solid phases; Sorbents; Species; Spectroscopy; Sulfur; Sulfur compounds; Thiophenes; Sulfur compounds; Atmospheric pressure chemical ionization; LC-MS; Ligand exchange chromatography; Methylation; Electrospray ionization
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2020.119783

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•Plenty of protocols were compared to extract and fractionate sulfur-containing compounds.•LEC/Si-Ag+ allows an efficient separation between thiophenes and sulfides.•LEC/Si-Cu2+ allows an efficient extraction and separation of disulfides.•LEC/MIP provides the extraction of the highest amount of sulfur compounds.•HPLC/APCI (+) Orbitrap MS allows expanding the chemical composition of S-Compounds.
Extraction and fractionation of sulfur-containing compounds from vacuum gas oil were carried out by using non-reactive methods such as ligand exchange chromatography (LEC) on solid-phase extraction cartridges and a molecularly imprinted polymer (MIP). All fractions obtained by these methods were methylated, and sulfur compounds (S1) were analyzed as methyl sulfonium ions [M + CH3]+ by positive-ion ESI Orbitrap mass spectrometry. LEC on strong cation exchange sorbents modified with Ag+ (SCX-Ag+) and Cu2+ (SCX-Cu2+) cations isolate sulfides and thiophenes through complexation of the sulfur atoms with the metal cations. In contrast, LEC on the stationary silica phase modified with Ag+ cations (Si-Ag+) was selective of sulfur species (S1) with higher DBE values near the planar limit. Interestingly, LEC/SCX-Cu2+ allowed the extraction of disulfides and other sulfur compound classes such as OS and OS2 detected as [M + H]+. Among LEC separations, the Si-Ag+ provides the largest number of molecular assignments (565) of sulfur species (S1) followed by SCX-Ag+ and SCX-Cu2+ with 463 and 408 formulae, respectively. On the other hand, a polymer with dibenzothiophene molecules imprinted afforded the highest number (820) of molecular formulae (CcHhS1) with a wider DBE ~1–20 and carbon number ~30–70 in comparison with the species (S1) eluted by LEC methods. A further separation by online HPCL/APCI (+) Orbitrap MS of the fractions obtained by SCX-Ag+ allows detecting sulfur compounds with DBE values up to 23. This contribution provides alternatives for the isolation and fractionation of sulfur-containing compounds that may be extended to heavy crude oil and asphaltenes.