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 dicarbonylic products obtained in the photo-oxidation of furan, 2-methylfuran and 3-methylfuran in the presence of HONO: butenedial, 4-oxo-2-pentenal and 2-methylbutenedial, respectively. The combination of the methodology of SPME in the furan systems holds great potential in the elucidation of aspects of the chemistry of 1,4-dicarbonyls unknown to date. This methodology can accomplish discriminated quantification of the cis and trans isomers. The use of PTR-MS applied to the same purpose is also presented and the advantages of the combined use of the two methodologies discussed. The experiments were carried out in the outdoors simulation chambers EUPHORE. 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. Yields of other products, i.e., formaldehyde, glyoxal, maleic anhydride and formic acid in the furan experiments and also methylglyoxal (in the case of the methyl derivatives) are also provided. Most of these were secondary products formed from the subsequent degradation of the 1,4-dicarbonyls. Furthermore, the 1,4-dicarbonyls have also been identified in the chemical characterization 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.JRC.H.2-Climate chang

Atmospheric Chemistry of C3-C6 Cycloalkanecarbaldehydes

The rate coefficients for the gas phase reaction of NO3 and OH radicals with a series of Cycloalkanecarbaldehydes have been measured in purified air at 298 ± 2 K and 760 ± 10 Torr by the relative rate method using a static reactor equipped with long-path FT-IR detection. The values obtained for the OH radical reactions (in units of 10-11 cm3 molecule-1 s-1) were: cyclopropanecarbaldehyde, 2.13 ± 0.05; cyclobutanecarbaldehyde, 2.66 ± 0.06; cyclopentanecarbaldehyde, 3.27 ± 0.07; cyclohexanecarbaldehyde, 3.75 ± 0.05. The values obtained for the NO3 radical reactions, (in units of 10-14 cm3 molecule-1 s-1) were: cyclopropanecarbaldehyde, 0.61 ± 0.04; cyclobutanecarbaldehyde, 1.99 ± 0.06, cyclopentanecarbaldehyde 2.55 ± 0.10; cyclohexanecarbaldehyde, 3.19 ± 0.12. Furthermore, the reaction products with OH have been investigated using long-path FT-IR spectroscopy and proton-transfer-reaction mass spectrometry (PTR-MS). The identified products cover a wide spectrum of compounds including nitroperoxycarbonyl cycloalkanes, cycloketones, cycloalkyl nitrates, multifuntional compounds containing carbonyl, hydrosy and nitrooxy funtional groups, HCOOH, HCHO, CO and CO2.JRC.H.2-Climate chang

Comparison of Atmospheric Pressure Chemical Ionization and Field Ionization Mass Spectrometry for the Analysis of Large Saturated Hydrocarbons

Direct infusion atmospheric pressure chemical ionization mass spectrometry (APCI-MS) was compared to field ionization mass spectrometry (FI-MS) for the determination of hydrocarbon class distributions in lubricant base oils. When positive ion mode APCI with oxygen as the ion source gas was employed to ionize saturated hydrocarbon model compounds (M) in hexane, only stable [M – H]⁺ ions were produced. Ion–molecule reaction studies performed in a linear quadrupole ion trap suggested that fragment ions of ionized hexane can ionize saturated hydrocarbons via hydride abstraction with minimal fragmentation. Hence, APCI-MS shows potential as an alternative of FI-MS in lubricant base oil analysis. Indeed, the APCI-MS method gave similar average molecular weights and hydrocarbon class distributions as FI-MS for three lubricant base oils. However, the reproducibility of APCI-MS method was found to be substantially better than for FI-MS. The paraffinic content determined using the APCI-MS and FI-MS methods for the base oils was similar. The average number of carbons in paraffinic chains followed the same increasing trend from low viscosity to high viscosity base oils for the two methods