The trace polar species present in diesel were investigated by combining selective ionization
with high resolution mass spectrometry. To eliminate matrix effects, the polar fraction was
extracted using methanol and direct infusion with electrospray ionization and mass analysis were
performed. The advantages and limitations of time-of-flight mass spectrometry and Fourier
transform ion cyclotron resonance mass spectrometry for diesel analysis were discussed.
Complementary information was obtained by considering both positive and negative ion mass
spectra in terms of compounds that form part of the inherent fuel composition and compounds
that represent fuel additives. Additionally, diluted fuels were separated by gas chromatography
prior to atmospheric pressure chemical ionization and mass analysis. Results showed that a large
portion of unsaturated polycyclic hydrocarbons were not detected during direct infusion
experiments, indicating that these species were not extracted efficiently with methanol and/or
ionized efficiently with electrospray.