Secondary ozonides of substituted cyclohexenes: a new class of pollutants characterized by collision-induced dissociation mass spectrometry using negative chemical ionization |
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Authors: | Nørgaard Asger W Nøjgaard Jacob K Clausen Per A Wolkoff Peder |
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Affiliation: | aIndoor Environment Group, National Research Centre for the Working Environment, Lersø Parkallé 105, DK-2100 Copenhagen Ø, Denmark |
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Abstract: | Recent studies indicate that secondary ozonides of cyclic alkenes are formed in atmospheric reactions and may be relatively stable. The secondary ozonides (SOZs) of cyclohexene (1), 1-methylcyclohexene (2), 4-isopropyl-1-methylcyclohexene (3) and 4-isopropenyl-1-methylcyclohexene (limonene) (4) have been characterized by rapid gas chromatography electron ionization (EI), negative and positive chemical ionization (CI: ammonia, isobutane and methane) and collision-induced dissociation (CID) mass spectrometry. Both EI and positive CI spectra were found unsuitable for reproducible analysis. However, negative CI showed stable (M−H)− ions with minor fragmentation. CID of the (M−H)− ions resulted in simple and reproducible fragmentation patterns for all four SOZs with loss of m/z 18, 44 and 60, tentatively assigned as H2O, CO2 and C2H4O2 or CO3, respectively. Thus, negative CI-MS–MS in combination with rapid gas chromatography is the preferred method for identification of secondary ozonides of cyclohexenes. |
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Keywords: | Indoor air Mass spectrometry Secondary ozonides Substituted cyclohexenes |
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