Reactions of Hydrated Hydronium Clusters

Ideally, if H3O+ is the chosen proton donor, then that should be the only ion reacting with the analyte gas in the drift tube of a PTR-MS instrument. In practice, the presence of unreacted water vapour from the ion source, from degassing of the walls of the drift tube, and from the analyte gas, inevitably leads to some formation of cluster ions of the type H3O + (H20) via the general process 

The rate coefficient for the reaction between hydrated hydronium (H30+(H20) ) and acetaldehyde decreases as the number of water molecules, n, increases, as illustrated in Table 2.5. One factor that contributes to this decrease is an increase in the reduced mass of 

---

Proton Transfer Reaction Mass Spectrometry 2.2.4.2 Reactions of Hydrated Hydronium Clusters... 

---