Time-of-flight ion mobility spectrometry in combination with laser-induced fluorescence detection system

A laser-induced fluorescence (LIF) was used as a complimentary detection system for time-of-flight ion mobility spectrometry (TOF-IMS). A LIF detection system is potentially faster than a conventional electrometer detector and can provide additional (to usual for IMS drift time) analytical information, namely wavelength of fluorescence maxima and fluorescence lifetime. Therefore, better discrimination ability can be expected. Additionally, the combination of IMS and LIF operates at atmospheric pressure. This allows fluorescence measurements of specified ions and ion clusters, which would not survive in a mass spectrometer. An IMS drift cell of open design with both the electrometer and LIF detectors was designed. The feasibility of IMS-LIF was demonstrated on the example of the Xanthene dye Rhodamine 6G (R6G). Electrospray was used as an ionization source. The release and desolvation of R6G ions from the electrospray with following IMS-LIF analysis were demonstrated. The effects of experimental parameters (e.g., ion gate and drift voltages, distance to ESI emitter) are demonstrated and discussed. The obtained results are promising enough to ensure the potential of LIF as a complimentary/alternative detection system for time-of-flight ion mobility spectrometry.