Laser desorption ionization of compounds that absorb 337 nm (e.g., vitamin B<sub>12</sub> and selected porphyrins) are examined by using Fourier transform ion cyclotron resonance (FTICR) mass spectrometry. The experiments are performed by mixing the sample with a host compound that promotes desorption and/or ionization. The relative abundance of photofragment ions can be controlled by simple adjustments of parameters such as the laser power and matrix-to-analyte ratio. In addition, it is shown that gas-phase photoionization/photodissociation of laser-desorbed species by a second laser pulse provides structural information for both negative and positive ions.
Touradj Solouki and David H. Russell, "Structural Mass Spectrometry of Matrix-Assisted Laser-Desorbed Biomolecules by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry: Photoionization and Photofragmentation," Appl. Spectrosc. 47, 211-217 (1993)