Formation of polyketones in irradiated toluene/propylene/NOx/air mixtures

A laboratory study was carried out to investigate the formation of polyketones in secondary organic aerosol from photooxidation of the aromatic hydrocarbon toluene, a major constituent of automobile exhaust. The laboratory experiments consisted of irradiating toluene/propylene/NOx/air mixtures in a smog chamber operate in the dynamic mode and collecting submicron secondary organic aerosol samples on Zefluor filters and on stainless steel disks in a low pressure cascade impactor. Carbonyl oxidation products in methanol extracts of the filters were derivatized using O-(2,3,4,5,6,-pentafluorobenzyl)-hydroxylamine, and the oxime derivatives were detected with a positive chemical ionization gas chromatography ion trap mass spectroscopy (GC-ITMS) system. Infrared spectra of the cascade impactor samples were used to determine the chemical functional group concentrations of the aerosol. The results of the GC-ITMS and infrared spectral analyses were consistent with the formation of multifunctional oxygenates, including hydroxy diones as well as triones, tetraones, and pentaones.