Proton affinity of Peroxyacetyl nitrate sampled by membrane introduction mass spectrometry

Peroxyacetyl nitrate (PAN) is a fragile, highly reactive molecule which has proven difficult to characterize by mass spectrometry. This study investigates the use of a membrane introduction system to sample PAN and demonstrates that the molecular ions [M+H]⁺, [M+H]^- and M(-·) can be generated under chemical ionization conditions. Use of tandem mass spectrometry provides characteristic spectra. These capabilities are applied to generate adduct ions of PAN with reference compounds of known proton affinity. Collision induced dissociation of these ions gives, by application of the kinetic method relationship, an estimated value of 191 ± 3 kcal/mol (798 ± 12 kJ/mol) for the proton affinity of PAN.