Introduction Field desorption (FD) is an ionization method that utilizes electron tunneling in a high electric field near the emitter surface or whisker tip. Sample is applied directly on to the emitter and is then heated by applying an electric current through the emitter for desorption and ionization. FD has been used to analyze nonvolatile compounds, polymers, etc. as a soft ionization method that produces intact molecular ions with very few fragment ions in most cases. In this work, we used FD to analyze several quaternary borate ammonium salts that are designed as photoinitiators for the polymerization of functional polymers.