Cryogenic Gas-phase IR Spectroscopy on a Commercial Ion Mobility-Mass Spectrometry Platform

The combination of gas-phase infrared (IR) spectroscopy with ion mobility spectrometry and mass spectrometry provides detailed, multidimensional structural information that facilitates the identification of unknown analytes. The instrumentation for performing these measurements is typically home-built and requires substantial expertise to operate. Here, we demonstrate messenger-tagging IR spectroscopy on a modified Synapt G2-S ion mobility-mass spectrometer (IM-MS). Messenger-tagging is performed in a commercially available cryogenic ion trap inserted between the exit of the transfer cell and the TOF pusher assembly, and tagged ions are excited by IR light before MS measurement. We report the adjustments to the timing cycle and voltage gradient in the Synapt G2-S necessary for efficient trapping and messenger-tagging in the cryogenic trap. The capabilities of this instrument are demonstrated by measuring IM-MS-IR data for leucine enkephalin, a benchmark standard in mass spectrometry. The ability to selectively transmit ions of specific mobility enables the separation and subsequent IR spectroscopy of the isomeric trisaccharides cellotriose and melezitose. These data demonstrate the first implementation of messenger-tagging IR spectroscopy in a widely used, commercially available IM-MS system. The user-friendly implementation of these techniques overcomes a significant barrier to the widespread incorporation of orthogonal IR spectroscopy measurements in existing IM-MS workflows and will aid in distinguishing unknown molecules in untargeted -omics measurements.