| Title: | "Ternary association reactions of H(3) O(+) , NO(+) and O(2) (+*) with N(2) , O(2) , CO(2) and H(2) O; implications for selected ion flow tube mass spectrometry analyses of air and breath" |
| Address: | "J. Heyrovsky Institute of Physical Chemistry of the Czech Academy of Sciences, Prague, Czech Republic" |
| Journal Title: | Rapid Commun Mass Spectrom |
| ISSN/ISBN: | 1097-0231 (Electronic) 0951-4198 (Linking) |
| Abstract: | "RATIONALE: The reactions of the reagent ions used for trace gas analysis in selected ion flow tube mass spectrometry (SIFT-MS), R(+) , viz. H(3) O(+) , NO(+) and O(2) (+) , with the major gases in air and breath samples, M, viz. N(2) , O(2) , CO(2) and H(2) O, are investigated. These reactions are seen to form weakly-bound adduct ions, R(+) M, by ternary association reactions that must not be mistaken for genuine volatile organic compound (VOC) analyte ions. METHODS: The ternary association rate coefficients mediated by helium (He) carrier gas atoms, k(3a) , have been determined for all combinations of R(+) and M, which form R(+) M adduct ions ranging in m/z from 47 (H(3) O(+) N(2) ) to 76 (O(2) (+*) CO(2) ). This was achieved by adding variable amounts of M (up to 0.5 mbar pressure) into the He carrier gas (pressure of 1.33 mbar) in a SIFT-MS flow tube at 300 K. Parabolic curvature was observed on some of the semi-logarithmic decay curves that allowed the rate coefficients mediated by M molecules, k(3b) , to be estimated. RESULTS: Values of k(3a) were found to range from 1 x 10(-31) cm(6) s(-1) to 5 x 10(-29) cm(6) s(-1) , which form mass spectral R(+) M 'ghost peaks' of significant strength when analysing VOCs at parts-per-billion concentrations. It was seen that the R(+) M adduct ions (except when M is H(2) O) react with H(2) O molecules by ligand switching forming the readily recognised monohydrates of the initial reagent cations R(+) H(2) O. Whilst this ligand switching diminishes the R(+) M adduct ghost peaks, it does not eliminate them entirely. CONCLUSIONS: The significance of these adduct ions for trace gas analysis by SIFT-MS in the low m/z region is alluded to, and some examples are given of m/z spectral overlaps of the R(+) M and R(+) H(2) O adduct cations with analyte cations of VOCs formed by analysis of complex media like exhaled breath, warning that ghost peaks will be enhanced using nitrogen carrier gas in SIFT-MS" |
| Keywords: | Air/*analysis Breath Tests Carbon Dioxide/*chemistry Humans Ions/*chemistry Mass Spectrometry Nitric Oxide/*chemistry Oxygen/*chemistry Reactive Oxygen Species/*chemistry Volatile Organic Compounds/chemistry Water/*chemistry; |
| Notes: | "MedlineSmith, David Spanel, Patrik eng 21-25486S/Grantova Agentura Ceske Republiky/ Czech Science Foundation/ England 2021/12/15 Rapid Commun Mass Spectrom. 2022 Mar 30; 36(6):e9241. doi: 10.1002/rcm.9241" |
