Cations Derived from Fentanyls Generated by Atmospheric Pressure Photoionization in the Presence of Ammonia: An...

A set of fentanyl molecules when subjected to vacuum UV atmospheric pressure photoionization (VUV-APPI) in the presence of dopants (ammonia and anisole) shows two major bands in the ion mobility-mass spectrometry (IMS-MS) spectrum corresponding to (a) the protonated fentanyl, [M+H]⁺ and (b) a unique [M-74]⁺ ion. For the parent fentanyl, the [M-74]⁺ ion is at m/z 262 but, in the absence of ammonia, the product ion is shifted to m/z 245, corresponding to a difference of NH₃. Collision-induced dissociations (CID) of the [M-74]⁺ ions for all the different fentanyls examined here show the same pattern of neutral losses, namely NH₃ and HN=CH₂, and the dominant product ion is at m/z 84 (shifted to m/z 98 for 3-methylfentanyl and m/z 142 and 231 for carfentanyl). Dissociation of the [M-74-NH₃]⁺ ion derived from the fentanyls yields the same product ions as found in the electron impact (EI) ionization spectra of the fentanyls. The dissociation products of the [M-74-HN=CH₂]⁺ ion are different, include the ion at m/z 84, and correspond to the fragmentation products of protonated norfentanyls. Theoretical modeling supports the opening of new fragmentation channels as a result of the reaction of the initially formed iminium cation with ammonia at atmospheric pressure.