Unsaturated dicarbonyl products from the OH-initiated photo-oxidation of furan, 2-methylfuran and 3-methylfuran

This study presents the application of O-(2,3,4,5,6)-pentafluorobenzyl-hydroxylamine hydrochloride (PFBHA) on-fibre derivatisation Solid Phase Microextraction (SPME) to the sampling and quantification of the unsaturated 1,4-dicarbonyl products obtained in the photo-oxidation of furan, 2-methylfuran and 3-methylfuran with HONO: butenedial, 4-oxo-2-pentenal and 2-methylbutenedial, respectively. The use of Proton Transfer Reaction Mass Spectrometry (PTR-MS) is also considered and the advantages of the combined use of both methodologies is discussed. The 1,4 unsaturated dicarbonyl products sampled by SPME were quantified by GC-FID.The experiments were carried out in the EUPHORE outdoor simulation chambers. The results confirm that 1,4-dicarbonyls are the main products of the OH-initiated oxidation of furan and its methylated derivatives, a fact with environmental implications. Molar yields of (1.09 ± 0.41) and (0.90 ± 0.36) were obtained in two experiments of furan photo-oxidation. The yields of 4-oxo-2-pentenal and methylbutenedial were estimated to be (0.60 ± 0.24) and (0.83 ± 0.33) respectively, assuming the same SPME response factor as for butenedial. Furthermore, the unsaturated 1,4-dicarbonyls have also been identified in the chemical characterisation of the aerosols formed in the reactions. The yield of aerosols quantified were (8.5 ± 0.8)% in the photo-oxidation of furan, (1.85 ± 0.18)% in the photo-oxidation of 2-methylfuran and (5.5 ± 0.5)% in the photo-oxidation of 3-methylfuran, at the following concentrations of their precursors: 829 ± 249 ppbV and 748 ± 224 (in two furan experiments), 633 ± 190 in the 2-methylfuran and 641 ± 192 ppbV in the 3-methylfuran experiment.