Radikalizace hmotnostního spektrometru – OAD-TOF (8. Česká lipidomická a metabolomická konference)

Importance of the topic

The detailed structural analysis of lipids is crucial for understanding biological functions and disease mechanisms. Oxygen Attachment Dissociation (OAD) combined with high-resolution time-of-flight mass spectrometry provides a sensitive and selective approach to locate double bonds in complex lipid species, overcoming limitations of traditional collision-induced dissociation.

Objectives and study overview

• Introduce the OAD-TOF system based on Shimadzu LCMS-9050.
• Explain the underlying OAD principle and hardware configuration.
• Demonstrate applications in lipidomics, including isomer differentiation.

Methodology and Instrumentation

• LCMS-9050 QTOF system:
  
  • Sensitivity: S/N 10000:1 (1 pg Reserpine).
  • Resolution: 45 000 FWHM.
  • Mass range: m/z 10–40 000, mass accuracy <1 ppm.
  • Fast positive/negative switching (500 ms), MS/MS up to 200 Hz.
• OAD kit and radical source:
  
  • Microwave discharge heating of water vapor to generate O/OH radicals.
  • Collision cell guiding radicals to selectively cleave C=C bonds.
  • LabSolutions software for OAD/CID switching.
• Complementary techniques:
  
  • Probe electrospray ionization (PESI) for direct lipid analysis.
  • Supercritical fluid chromatography (SFC) for separation of free fatty acid isomers.

Main results and discussion

• OAD-MS/MS spectra pinpoint double bond positions in both positive and negative modes.
• OAD differentiates multiple C=C isomers in phospholipids (e.g., PC 36:4 side-chain localization) where CID alone is insufficient.
• Selective radical-driven fragmentation yields diagnostic fragments (n-6, n-9, n-12, n-15) for accurate mapping of unsaturations.
• Integration with MS-DIAL and MS-RIDD enables automated lipid annotation down to double bond positions.
• PESI-OAD-TOF allows rapid profiling of lipids in complex samples like butter.
• SFC-OAD-TOF separates and identifies free fatty acid isomers that co-elute in LC.

Benefits and practical applications

• Precise localization of C=C bonds enhances lipidomics and biomarker discovery.
• Non-lipid-specific adduct independence improves robustness compared to ozonolysis-based methods.
• High-throughput compatibility with data processing tools for comprehensive structural identification.
• Applicability across diverse sample types: tissues, food matrices, complex lipid mixtures.

Future trends and possibilities

• Integration with other ambient ionization methods and real-time analysis workflows.
• Expansion to broader compound classes beyond lipids, including natural products and pharmaceuticals.
• Advancements in software for automated radical-driven fragmentation interpretation.
• Miniaturization and field-deployable OAD-enabled mass spectrometers for on-site analysis.

Conclusion

The OAD-TOF platform effectively resolves unsaturation patterns in complex lipids, offering unmatched selectivity and sensitivity. Its seamless integration with high-resolution TOF instrumentation and data processing tools positions it as a powerful tool for in-depth lipid structural analysis across research and industrial applications.

References

• No explicit references provided in the source document.