An ion mobility mass spectrometer has been modified to allow optical interrogation of ions with different mass-to-charge (m/z) ratios and/or mobilities (K). An ion gating and trapping procedure has been developed which allows us to store ions for several seconds enabling UV photodissociation (UVPD).
The instrument has been modified to enable overlap of the laser and the ion beam within the transfer cell region. A CaF2 window is installed on the upper vacuum flange of the time-of-flight (ToF) analyser and a custom size UV-enhanced aluminium coated reflecting mirror (Melles Griot, USA) is attached to a modified pusher assembly. This mirror is mounted at a 45 degree angle with respect to the ion beam direction. In this configuration the laser beam is collinear with the ion beam. A lens has been added in the optical path, creating a focal point at the entrance of the transfer cell (between the parts 6 and 7. This modification retains all the normal functionality of the Q-ToF analyser. The laser used for this study was a Continuum Minilite II set at 266 nm with a repetition rate of 10 Hz. The energies used range between 0.4 and 1 mJ per pulse. The overall transmission of the energy between the output of the laser and the entrance of the transfer cell was measured as 50%.
UV photodissociation of trapped ions following ion mobility separation in a Q-ToF mass spectrometerAnalyst, 2014,139, 6348-6351DOI: 10.1039/C4AN01656D