FA-SIFT study of the reactions of H3O+·(H2O)n (n = 0, 1, 2), NO+ and O2radical dot+ with the terpenoid aldehydes citral, citronellal and myrtenal and their alcohol analogues
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Biogenic volatile organic compounds (BVOCs) significantly contribute to atmospheric chemistry, air quality and climate. On-line detection of these compounds can be performed by Selected Ion Flow Tube-Mass Spectrometry (SIFT-MS), provided the rate constants and product ion distributions of the underlying ion/molecule reactions are known. These parameters are presented for the reactions of the SIFT-MS reagent ions H3O+·(H2O)n (n = 0–2), NO+ and O2radical dot+ with the terpenoid aldehydes citral, citronellal and myrtenal and the terpenoid alcohols citronellol and myrtenol. The experiments were performed at 295 K and 1.5 hPa in a Flowing Afterglow Selected Ion Flow Tube (FA-SIFT) instrument. All studied reactions proceed at the collision rate which is beneficial for the BVOC detection sensitivity. Non-dissociative proton transfer, and elimination of a water molecule or simultaneous ejection of a water molecule and C4H8 following protonation were observed as the major mechanisms for most H3O+ reactions. Reactions of H3O+·(H2O) mainly proceeded by non-dissociative proton transfer, possibly followed by ejection of a water molecule, whereas the main observed mechanism for H3O+·(H2O)2 reactions was ligand switching followed by elimination of up to three water molecules. Charge transfer occurred for all NO+ reactions and was accompanied by other major mechanisms such as hydride transfer and/or elimination of a water molecule following charge transfer and/or ternary association. The O2radical dot+ reactions generally resulted in strong fragmentation. The product ion distributions suggest that selective detection of some isomeric terpenoids might be possible. However, interference with simultaneously emitted monoterpenes could be a problem.
CitationAmelynck, C.; Mees, B.; Schoon, N.; Bultinck, P. (2015). FA-SIFT study of the reactions of H3O+·(H2O)n (n = 0, 1, 2), NO+ and O2radical dot+ with the terpenoid aldehydes citral, citronellal and myrtenal and their alcohol analogues. , International Journal of Mass Spectrometry, Vol. 379, 52-59, DOI: 10.1016/j.ijms.2014.12.005.