Session: Advances in Mass Spectrometry:

Laser desorption ionization (LDI) is a soft ionization technique that uses organic acid matrices or other materials (nanoparticles) to absorb incident energy from the laser to facilitate desorption/ionization. Gold nanoparticles (AuNPs) are increasingly being explored for the interesting photophysical properties. In addition to ionization of intact molecules, we have observed unique fragmentation of diphenhydramine, including patterns that mimic electron impact (EI) ionization, a hard ionization technique. Here, we further explore the secondary gas-phase reactions that may be occuring, including those initiated by radicals, specifically hydroxyl radicals. Simple bond cleavages that match the electron impact (EI) mass spectrum suggests that internal energy redistribution drives much of this fragmentation pattern. In addition to fragmentation, secondary radical reactions result in additional species. Diphenhydramine reacts with hydroxyl radicals to give secondary products. Continuing this research on fragmentation and radical reactions, we have looked at diphenhydramine analogues and known gas-phase radical promoters to manipulate the gas-phase secondary reactions. Fragmentation is consistent for these additional analytes and hydroxyl radical reactions occur, with ring opening reactions as well as simple hydroxyl additions. TEMPO and iron ions were added to determine the affect of radical scavengers on fragmentation reactions.

Dr. Katherine Stumpo

Associate Professor of Chemistry, University of Scranton

Appearances