Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 3 4 2003 10.5194/acpd-3-4359-2003 http://www.atmos-chem-phys-discuss.net/3/4359/2003/ http://www.atmos-chem-phys-discuss.net/3/4359/2003/acpd-3-4359-2003.html http://www.atmos-chem-phys-discuss.net/3/4359/2003/acpd-3-4359-2003.pdf 4359 4391 2003-08-01 Measurements of photo-oxidation products from the reaction of a series of alkyl-benzenes with hydroxyl radicals during EXACT using comprehensive gas chromatography J. F. Hamilton A. C. Lewis C. Bloss V. Wagner A. P. Henderson B. T. Golding K. Wirtz M. Martin-Reviejo M. J. Pilling University of Leeds, Department of Chemistry, Woodhouse Lane, Leeds, LS2 9JT, UK University of York, Department of Chemistry, Heslington, York, YO10 5DD, UK School of Natural Sciences – Chemistry, Bedson Building, University of Newcastle upon Tyne, Newcastle upon Tyne NEI 7RU, UK Fundaci´on Centro de Estudios Ambientales del Mediterráneo (CEAM), EUPHORE laboratories, C/Charles Darwin, 14 Parc Technológico, Paterna, Valencia, Spain Photo-oxidation products from the reaction of a series of alkyl-benzenes, (benzene, toluene, p-xylene and 1,3,5-trimethyl-benzene) with hydroxyl radicals in the presence of  NOx have been investigated using comprehensive gas chromatography (GCXGC). A GCXGC system has been developed which utilises valve modulation and independent separations as a function of both volatility and polarity. A number of carbonyl-type compounds were identified during a series of reactions carried out at the European Photoreactor (EUPHORE), a large volume outdoor reaction chamber in Valencia, Spain. Two litre chamber air samples were cryo-focused, with a sampling frequency of 30 min, allowing the evolution of species to be followed over oxidation periods of 3–6 h. To facilitate product identification, several carbonyl compounds, which were possible products of the photo-oxidation, were synthesised and used as reference standards. For toluene reactions, observed oxygenated intermediates found included the co-eluting pair a-angelicalactone/4-oxo-2-pentenal, maleic anhydride, citraconic anhydride, benzaldehyde and p-methyl benzoquinone. In the p-xylene experiment, the products identified were E/Z-hex-3-en-2,5-dione and citraconic anhydride. For 1,3,5-TMB reactions, the products identified were 3,5-dimethylbenzaldehyde, 3,5-dimethyl-3H-furan-2-one and 3-methyl-5-methylene-5H-furan-2-one. Preliminary quantification was carried out on identified compounds using liquid standards. Comparison of FTIR and GCXGC for the measurement of the parent aromatics generally showed good agreement.