Evaluation of Collision Cross Section Calibrants forStructural Analysis of Lipidsby Traveling Wave Ion Mobility-Mass Spectrometry

摘要

Collision cross section (CCS) measurement of lipids using traveling wave ion mobility-mass spectrometry (TWIM-MS) is of high interest to the lipidomics field. However, currently available calibrants for CCS measurement using TWIM are predominantly peptides that display quite different physical properties and gas-phase conformations from lipids, which could lead to large CCS calibration errors for lipids. Here we report the direct CCS measurement of a series of phosphatidylcholines (PCs) and phosphatidylethanolamines (PEs) in nitrogen using a drift tube ion mobility (DTIM) instrument and an evaluation of the accuracy and reproducibility of PCs and PEs as CCS calibrants for phospholipids against different classes of calibrants, including polyalanine (PolyAla), tetraalkylammonium salts (TAA), and hexakis(fluoroalkoxy)phosphazines (HFAP), in both positive and negative modes in TWIM-MS analysis. We demonstrate that structurally mismatched calibrants lead to larger errors in calibrated CCS values while the structurally matched calibrants, PCs and PEs, gave highly accurate and reproducible CCS values at differenttraveling wave parameters. Using the lipid calibrants, the majorityof the CCS values of several classes of phospholipids measured byTWIM are within 2% error of the CCS values measured by DTIM. The developmentof phospholipid CCS calibrants will enable high-accuracy structuralstudies of lipids and add an additional level of validation in theassignment of identifications in untargeted lipidomics experiments.