Using a dual inlet atmospheric pressure ionization source as a dynamic reaction vessel.

Atmospheric pressure ionization (API) sources have the ability to serve as dynamic 'reaction vessels' and this capability has been rapidly evolving over the past few years. With API sources, many different reagents and source conditions can be rapidly explored with minimal carryover or contamination of the mass spectrometer. While most API applications involve the simple protonation/deprotonation of analyte molecules, a great deal of flexibility and utility is available in almost any API source, provided the reagents and ionization conditions are judiciously selected. Here, the generation of a unique and useful class of reagent ions at atmospheric pressure is demonstrated for the first time. Within the AP gas-phase environment of a dual inlet ion source, the gas-phase synthesis of substituted N-phenylpyridinium cations is demonstrated by establishing conditions favorable to the nucleophilic substitution reaction required for their formation. The flexibility of this API source as a reaction vessel is also demonstrated.