Instrumental response as a function of aromaticity and fuel type

Low voltage (10 ev) electron impact mass spectrometric (LV/EI/MS) methods are widely used to determine aromatic hydrocarbon distributions in petroleum and other samples, because the spectra contain predominantly molecular ions. For fossil fuel samples, containing mainly highly alkylated and cycloalkylated polycyclic aromatic hydrocarbons (PAH), a uniform molar response is typically assumed because only a fraction of these compound types have known MS sensitivities. This approximation introduces significant errors. Because of the impracticality of determining individual sensitivities of all aromatic species potentially in fuels, the purpose of this study was to determine average LV/EI/MS responses of well characterized fractions from a wide range of fuel types and boiling ranges. This approach has yielded results consistent with expected trends in MS sensitivities with aromaticity and degree of alkylation