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The compositions of volatile compounds in headspace (HS) analyzed by a solid phase microextraction (SPME) sampling method usually differ from true compositions mainly because the partition coefficients of these compounds between headspace and a SPME fiber are not equal. In this paper we report an analytical strategy to more accurately quantify relative compositions of selected hydrocarbons present in gasoline residue by employing inverse gas chromatography (IGC) coupled with a HS-SPME sampling method. First, IGC measurements using a column packed with a solid support coated with polydimethylsiloxane (PDMS) were conducted to obtain the thermodynamic and chromatographic data needed for the estimation of the relative partition coefficients of n-heptane, toluene, and 1,2,4-trimethylbenzene (TMB) between headspace and a PDMS SPME fiber at 100 and 130 °C. Then, chemical analysis of headspace containing different compositions of vaporized n-heptane, toluene, and TMB were carried out via a PDMS SPME sampling method at 100 and 130 °C. Finally, the relative compositions of these vaporized compounds in headspace were estimated using compositions from a PDMS SPME sampling method and the relative partition coefficients from IGC. Our results showed that the estimated relative compositions of these compounds in headspace are comparable to true compositions obtained from direct headspace vapor analysis within reasonable relative errors.