Using XCiMS to Quantify the Benefits of Ion Mobility Spectrometry for Untargeted Metabolomics

In human plasma, ion mobility spectrometry (IMS) with LC-MS resolves up to 50% more 4D peaks than LC-MS 3D peaks, but few correspond to newly resolved structural isomers.

• Why it matters: IMS could improve untargeted metabolomics, yet benefits have been hard to quantify because software has lacked workflows enabling direct comparison of LC-IMS-MS with LC-MS data.
• What they did: XCiMS collapses 4D LC-IMS-MS data into pseudo-3D for peak detection, then extracts 4D signals from 3D-guided regions of interest; it was applied to human plasma.
• The result: IMS mostly increases features via charge isomers and ion clusters, and with a 16-minute chromatographic separation it decreases chimeric MS/MS frequency by about half while providing CCS values for library searching.