Monoaromatic complexity in urban air and gasoline assessed using comprehensive GC and fast GC-TOF/MS

Two state-of-the-art analytical techniques have been used to assess monoaromatic complexity in gasoline, gasoline vapours and urban air. A comparison of comprehensive gas chromatography (GC×GC) and fast gas chromatography—time-of-flight mass spectrometry (GC-TOF/MS) has been made, with emphasis on the ability of each technique to speciate at high isomeric complexity. The high spectral acquisition rates from TOF/MS gave improved peak deconvolution of overlapping analytes when compared to standard quadrupole configurations, with 89 monoaromatic isomers isolated in gasoline during a 200 s GC separation. Higher analytical resolution for gasoline was obtained using GC×GC, isolating 130 monoaromatics, using combined column retention behaviour for analyte identification. Analysis of urban air using GC×GC indicated the presence of 147 monoaromatic species with up to 8 carbon substituents on the ring. In conventional separations such as single column GC-FID, heartcut GC and GC/MS these compounds are hidden by the constant co-elutions occurring in low volatility regions. The vast number of low concentration species in the higher boiling point range make it impossible to completely speciate all analytes present using single column methodologies. Comparison of 2D GC×GC chromatograms for air and gasoline vapours demonstrated visually the impact of evaporative emission sources in urban environments. The potential contribution of larger monoaromatic compounds as precursors to both photochemical ozone and secondary organic aerosol is discussed along with the implications on modelling OH chemistry in polluted air.