Fragmentation pathways of selectively labeled propranolol using electrospray ionization on an ion trap mass spectrometer and comparison with ions formed by electron impact

Propranolol, deuterium‐ and 18O‐labeled propranolol and related compounds were analyzed using an ion trap mass spectrometer equipped with a modified Finnigan API electrospray interface. Sequential product ion (MSn) experiments were used to elucidate fragmentation pathways for these compounds. The observed ions were compared to those observed under electron impact (EI) conditions. The electrospray ionization (ESI) ion trap spectra, as well as the EI spectra, afford useful information to allow assignments of most product ions, many of which retain portions of the aliphatic three‐carbon side chain. Copyright © 1999 John Wiley & Sons, Ltd.