The residual concentration of DBT in

The mobile phase was a mixture of acetonitrile and water (80:20 v/v) with a flow rate of 1.8 mL/min. The formation of sulfone in oxidative desulfurization was confirmed using FTIR analysis of aliquots of reaction mixture in category B.2 (as a representative of all experimental protocols listed in Table 1) after completion of sonication. To identify the intermediates during DBT oxidation, GC–MS analysis of the same reaction sample was performed using Varian 240-GC equipped with VF-5 ms column (30 × 0.25 m ID DF = 0.25).