Capillary electrophoretic separation of polycyclic aromatic sulfur heterocycles

Area of Science:

• Analytical Chemistry
• Environmental Chemistry
• Petroleum Chemistry

Background:

• Polycyclic aromatic sulfur heterocycles (PASHs) are prevalent in fossil fuels and petroleum products.
• Accurate separation and analysis of PASHs are essential for understanding fuel composition and refining processes.
• Existing chromatographic methods have limitations in resolving complex PASH mixtures and their enantiomers.

Purpose of the Study:

• To develop and validate a capillary electrophoresis (CE) method for separating PASHs.
• To compare the resolution and efficiency of CE with gas chromatography (GC) and high-performance liquid chromatography (HPLC).
• To investigate the potential of CE for analyzing PASHs in real-world samples like desulfurized diesel fuel.

Main Methods:

• PASHs were derivatized via methylation or phenylation to impart an electric charge for CE separation.
• Capillary electrophoresis was employed, with comparisons made to reversed-phase liquid chromatography and capillary gas chromatography.
• Preconcentration techniques were used for analyzing PASHs in deeply desulfurized diesel fuel.

Main Results:

• CE demonstrated superior resolution for PASHs compared to reversed-phase liquid chromatography.
• The CE method successfully separated all monomethylbenzothiophenes, a feat not achieved by capillary gas chromatography.
• A linear correlation was established between migration time and the calculated molecular volume of the PASHs.
• Enantiomeric separation of derivatized PASHs was achieved by incorporating cyclodextrins into the running buffer.

Conclusions:

• Capillary electrophoresis is a highly effective technique for the separation of complex PASH mixtures.
• CE offers significant advantages in resolution and separation capability over conventional chromatographic methods for PASH analysis.
• The CE method, particularly with chiral selectors, provides a powerful tool for detailed characterization of PASHs in petroleum products and environmental samples.