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Updated: Dec 19, 2025
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Using a Cyclic Ion Mobility Spectrometer for Tandem Ion Mobility Experiments
Published on: January 20, 2022
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Resolving Isomers of Star-Branched Poly(Ethylene Glycols) by IMS-MS Using Multiply Charged Ions
Calvin A Austin1, Ellen D Inutan1, Brian C Bohrer2
1Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States.
Summary
Ion mobility spectrometry-mass spectrometry (IMS-MS) separates complex molecules by structure and charge. This study demonstrates IMS-MS can distinguish branched and linear poly(ethylene glycol) oligomers, offering a new analytical approach.
Area of Science:
- Analytical Chemistry
- Physical Chemistry
- Polymer Chemistry
Background:
- Ion mobility spectrometry-mass spectrometry (IMS-MS) separates ions based on size, charge, and shape.
- Separation of oligomeric structures can be enhanced by structural extension via cation repulsion.
- Differentiating branched structures from linear ones is crucial for polymer analysis.
Purpose of the Study:
- To demonstrate the capability of IMS-MS to separate multiply charged ions of star-branched poly(ethylene glycol) (PEG) oligomers.
- To investigate the influence of different cations and ionization methods on IMS-MS separation.
- To explore direct surface analysis using novel ionization techniques for spatially resolved measurements.
Main Methods:
- Utilized a home-built high-resolution electrospray ionization (ESI) IMS-MS instrument for structural characterization.
- Employed commercially available traveling wave IMS-MS instruments for broader applicability.
- Investigated matrix-assisted ionization from charged solid particles for direct surface analysis.
Main Results:
- Achieved well-resolved drift times for doubly charged ions, separating isomers of star-branched PEG oligomers.
- Successfully differentiated star-branched PEG from linear PEG oligomers.
- Demonstrated IMS-MS as a "snapshot" approach for visualizing architectural dispersity and purity.
Conclusions:
- IMS-MS effectively separates branched and linear PEG oligomers, regardless of ionization method (ESI or surface-based).
- Multiply charging enhances gas-phase separation, offering advantages over traditional methods like matrix-assisted laser desorption/ionization.
- Direct surface analysis via novel ionization methods provides potential for spatially resolved polymer characterization.
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