Molecular beam mass spectrometry (MBMS) and gas chromatography (GC) are complementary methods that provide a detailed description of flame structures. MBMS can measure most stable and reactive species but mass overlapping (isomers, species at same m/e), isotopic, and ionic fragmentation interferences can be solved by using GC. To improve species identification, an experimental technique coupling both mass spectrometry and GC is developed. Rich flat premixed ethylene/oxygen/argon flames (phi=2.25 and 2.50) have been investigated by both methods. After adequate calibrations, mole fraction profiles of several species measured by both techniques agree very well, but for methane, allene, propyne, and benzene, concentrations in burnt gases are somewhat larger when using GC than when using MBMS. C2H6, C2H4O, C3H6, and C3H8, which have similar masses as CH2O, CO2 or C3H8, CH2CO, and CO2, respectively, have been identified, separated, and calibrated by GC, which confirms that GC and MBMS are complementary techniques.