ASSESSMENT BY GAS-CHROMATOGRAPHY MASS-SPECTROMETRY OF HEXENES EMITTED TO AIR FROM PETROL

Hexenes and cyclohexenes in vapours of conventional petrol were separated by gas chromatography on an aluminium oxide column. All hexenes appear in a favourable chromatographic position between hexanes and heptanes. The seventeen isomeric acyclic hexenes were identified by mass spectra and single-ion monitoring on an ion-trap mass spectrometer. The rapidly photooxidant-forming isomers with a non-terminal double bond constitute 70% of the total amount of acyclic hexenes. The proportions of isomers in petrol vapour are similar to those in urban air and in exhaust from petrol-fuelled vehicles.