ANALYSIS OF LIPID SIGNALING CLASS ANALYTES USING A TRAVELLING WAVE CYCLIC ION MOBILITY SEPARATOR

Significance of the Topic

Lipid signaling molecules play vital roles in cell structure, energy storage and biochemical communication. Their structural diversity and frequent isobaric nature create significant analytical challenges in fields such as lipidomics, quality control and biomedical research. High resolution separations that distinguish subtle isomeric variations, including cis/trans double‐bond configurations, are essential for accurate identification and quantitation of these important biomolecules.

Objectives and Study Overview

This work evaluates the performance of a multi-pass travelling-wave cyclic ion mobility (cIM) separator coupled to a quadrupole time-of-flight mass spectrometer (Q-cIM-oaTOF). Key goals include: separation of lipid isomers (free fatty acids, glycerophosphocholines), cis/trans monounsaturated pairs, steroids and prostaglandins; assessment of resolution gains with increasing cIM passes; and demonstration of post‐IMS low-energy collision-induced dissociation (CID) for structural elucidation.

Methodology and Instrumentation

Sample preparation involved standard mixtures of free fatty acids (C14–C22), glycerophosphocholines and steroid/prostaglandin compounds dissolved in methanol/water with formic acid. Ion mobility–mass spectrometry data were acquired on a SELECT SERIES Cyclic IMS (Q-cIM-oaTOF) platform featuring a 98 cm RF ion guide with variable multi-pass travelling waves. Mobility separation was achieved by routing ions around the cyclic path for 1 to >20 passes, increasing Ω/ΔΩ resolution. Separated ions underwent low-energy CID in the transfer region, followed by time-of-flight mass analysis.

Key Results and Discussion

• Mono-unsaturated free fatty acids (C14–C22) with cis and trans double bonds were baseline separated by optimizing the number of cIM cycles; longer chains required more passes.
• Multiple double-bond fatty acids and glycerophosphocholines exhibited broader arrival time distributions and were only partially resolved.
• Steroid isomers (e.g., 21-deoxycortisol, corticosterone, 11-deoxycortisol) and prostaglandins (TxB2, 6k-PGF1α, 17-OHP, 21-OHP) were fully or partially separated at moderate resolution settings (<200 Ω/ΔΩ).
• Post-IMS CID spectra were successfully collected for all classes, enabling confident structural assignments and isomer discrimination.
• Two-dimensional cIM-MS plots demonstrated the ability to resolve trace contaminants and mixed analytes within a single experiment.

Benefits and Practical Applications

• Enhanced peak capacity and resolution for complex lipid mixtures improves confidence in isomer identification.
• Integration of mobility separation with MS/MS workflows supports detailed structural characterization in lipidomics and QA/QC.
• The variable resolution capability allows tailored analysis of small, rigid species versus larger, flexible molecules.

Future Trends and Potential Applications

• Extension of IMSn methodologies leveraging the cIM device for deeper fragmentation studies.
• Application to highly polyunsaturated and positional isomer mixtures encountered in clinical and environmental analyses.
• Integration with automated workflows and machine-learning algorithms for real-time lipidomics profiling.
• Development of standardized mobility libraries to support cross-platform identification of signaling lipids.

Conclusion

The SELECT SERIES Cyclic IMS system delivers adjustable, high-resolution separation of structurally similar lipid signaling analytes. Its multi-pass design enables targeted resolution of cis/trans and positional isomers across fatty acids, glycerophosphocholines, steroids and prostaglandins. Coupled with post-IMS CID, the platform provides a robust tool for comprehensive lipid structural analysis in research and quality assurance settings.

References

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