MASS SPECTROMETRY, GAS CHROMATOGRAPHY, AND COUPLING GC/MS AS COMPLEMENTARY TECHNIQUES FOR FLAME STRUCTURE ANALYSIS

Abstract

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 (φ = 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.

Keywords:

• mass spectrometry
• gas chromatography
• coupling GC/MS, ethylene flame

The authors are very grateful to the Ministère de la Région Wallonne (Belgium) for the financial support (grant nos. 98/41928, 99/42084, 00/42884, 01/43257, and 02/43371).