Protomers, or prototropic isomers, are protonation site isomers than can be resolved using ion mobility spectrometry. Dating back to their first report by Karpas et al. in 1990, decades of literature have studied their fundamental properties. Recently, our group and others have identified the presence of protomers for many fentanyl analogues, owing to their multiple basic sites. Currently, we are investigating the dependency on solvent and instrument conditions on the prevalence of these protomers, while also using mobility-aligned fragmentation to characterize them. We believe this approach also has significant promise for the identification of previously undetected drugs in the illicit market.

Representative Papers:

1. Determining protonation site in fentanyl protomers using ion mobility-aligned MS/MS fragmentation
2. Improved separation of fentanyl isomers using metal cation adducts and high-resolution ion mobility-mass spectrometry