Mapping and quantifying isomer sets of hydrocarbons ( ≥ C 12 ) in diesel exhaust, lubricating oil and diesel fuel samples using GC × GC-ToF-MS
Abstract. Airborne particles and vapours, like many other environmental samples including water,
soils and sediments, contain complex mixtures of hydrocarbons, often deriving
from crude oil either before or after fractionation into fuels, lubricants
and feedstocks. Comprehensive 2D gas chromatography time-of-flight mass
spectrometry (GC  ×  GC-ToF-MS), offers a very powerful technique that
separates and identifies many compounds in complicated hydrocarbon mixtures.
However, quantification and identification of individual constituents at high
ionization energies would require hundreds of expensive (when available)
standards for calibration. Although the precise chemical structure of
hydrocarbons does matter for their environmental impact and fate, strong
similarities can be expected for compounds having very similar chemical
structures and carbon numbers. There is, therefore, a clear benefit in an
analytical technique which is specific enough to separate different classes
of compounds and to distinguish homologous series while avoiding the need to
handle each isomer individually. Varying EI (electron impact) ionization mass
spectrometry significantly enhances the identification of individual isomers
and homologous compound groups, which we refer to as “isomer sets”.
Advances are reported in mapping and quantifying isomer sets of hydrocarbons
( ≥ C12 ) in diesel fuel, lubricating oil and diesel exhaust
emissions. By using this analysis we report mass closures of ca. 90 and
75 % for diesel fuel and lubricating oil, and identify 85 and 75 % of
the total ion current for gas- and particulate-phase diesel exhaust
emissions.