Development\nof a Platform for High-Resolution Ion\nMobility Separations Coupled with Messenger Tagging Infrared Spectroscopy\nfor High-Precision Structural Characterizations

The ability to uniquely identify a compound requires\nhighly precise\nand orthogonal measurements. Here we describe a newly developed analytical\nplatform that integrates high resolution ion mobility and cryogenic\nvibrational ion spectroscopy for high-precision structural characterizations.\nThis platform allows for the temporal separation of isomeric/isobaric\nions and provides a highly sensitive description of the ion’s\nadopted geometry in the gas phase. The combination of these orthogonal\nstructural measurements yields precise descriptors that can be used\nto resolve between and confidently identify highly similar ions. The\nunique benefits of our instrument, which integrates a structures for\nlossless ion manipulations ion mobility (SLIM IM) device with messenger\ntagging infrared spectroscopy, include the ability to perform high-resolution\nion mobility separations and to record the IR spectra of all ions\nsimultaneously. The SLIM IM device, with its 13 m separation path\nlength, allows for multipass experiments to be performed for increased\nresolution as needed. It is integrated with an Agilent qTOF MS where\nthe collision cell was replaced with a cryogenically held (30 K) TW-SLIM\nmodule. The cryo-SLIM is operated in a novel manner that allows ions\nto be streamed through the device and collisionally cooled to a temperature\nwhere they can form noncovalently bound N<sub>2</sub> complexes that\nare maintained as they exit the device and are detected by the TOF\nmass analyzer. The instrument can be operated in two modes: IMS+IR\nwhere the IR spectra for mobility-selected ions can be recorded and\nIR-only mode where the IR spectra for all mass-resolved ions can be\nrecorded. In IR-only mode, IR spectra (400 cm<sup>–1</sup> spectral\nrange) can be recorded in as short as 2 s for high throughput measurements.\nThis work details the construction of the instrument and modes of\noperation. It provides initial benchmarking of CCS and IR measurements\nto demonstrate the utility of this instrument for targeted and untargeted\napproaches.