Analysis of gasoline for aromatic hydrocarbons by GC/MS and by low-EV-HR/MS

The United States Clean Air Act requires that finished gasoline be formulated to reduce ozone-reactive emissions and to lower gasoline toxicity. Mandated changes in gasoline composition include limiting the concentrations of benzene and total aromatics, as well as other restrictions on composition and volatility. A set of guidelines published by the U.S. Environmental Protection Agency has specified GC/MS for determining total aromatics content. Based on the EPA guidelines, the American Society for Losting and Materials has proposed a standard method for determining aromatics in gasoline by GC/MS. In this laboratory, the ASTM gasoline samples have been analyzed by GC/MS in a magnetic-sector instrument equipped with a capillary column. In addition, they have been analyzed by low eV-high resolution mass spectrometry with sample introduction through an all-glass expansion-volume inlet. Nominal 10 eV electron ionization was used in the low eV analysis and 70 eV electron ionization in the GC/MS analysis. The high-resolution data were obtained at a resolving power of 10,000. For both methods, internal standards were included with the samples and calibration curves were calculated using least squares with a spreadsheet program. As a further check, liquid chromatography was used to analyze the samples for benzene and toluene.