Deep Ultraviolet Laser Ablation Electrospray Ion Mobility Mass Spectrometry

A solid-state deep ultraviolet (DUV) optical parametric oscillator (OPO) at 206 nm wavelength was utilized for laser ablation electrospray postionization of peptides and proteins coupled with ion mobility mass spectrometry (IM-MS) analysis. Peptide and protein standard solutions were spray deposited on quartz microscope slides to obtain thin, surface-coated dry films. The pulsed laser irradiated the solid sample biomolecules in transmission geometry, and the ablated surface material merged with the electrospray plume for ionization before entering the IM-MS instrument. Laser ablated biomolecules remained intact, and no fragmentation was observed from the peptide or protein standards. The efficiency of ionization was estimated at approximately 1% for instantaneous ion signal; however, the signal was not stable over time. Mass spectra of laser ablation electrospray for peptide and protein standards revealed multiply charged ions similar to those observed in direct electrospray ionization (ESI) MS. The ion mobility drift times for proteins from laser ablation electrospray (LA-ESI) experiments were indistinguishable from those observed in direct ESI.