Analytical procedures for the isolation of the sulfide and thiophene classes of compounds from fluid catalytic cracking (FCC) and residue fluid catalytic cracking (RFCC) gasoline are described. The methods are based on an effective composite extractant, sulfuric acid and water (SA-H2O), which has high efficiencies for extraction and recovery of sulfides from light petroleum fraction as well as FCC and RFCC gasoline. The sulfides and part of thiophenes in gasoline are separated and identified with the help of GC/FPD and GC/MS analysis, the contents of individual sulfides and thiophenes in FCC and RFCC gasoline were determined. (C) 2004 Elsevier Ltd. All rights reserved.