MS Imaging – DESI XS and SELECT SERIES MRT

Importance of the Topic

The combination of ambient ionization mass spectrometry imaging and ultra-high resolution analyzers addresses a critical need in spatially resolved chemical analysis of complex biological tissues. High mass resolution and accuracy enable unambiguous identification of lipids and small molecules without chromatographic separation, preserving spatial information and reducing sample preparation.

Study Objectives and Overview

This work evaluates the performance of the new SELECT SERIES MRT mass spectrometer coupled with the DESI XS ion source for imaging mouse brain sections. The aim is to demonstrate enhanced sensitivity, mass resolving power, and mass accuracy for confident mapping of endogenous lipids in tissue slices.

Methodology

Mouse brain transverse sections (16 µm) were analyzed by DESI imaging in positive ion mode. Samples were mounted without prior separation, stained post-acquisition with H&E to correlate morphology.

Použitá instrumentace

• DESI XS ambient ion source with heated transfer line (330 °C)
• SELECT SERIES MRT quadrupole multi-reflecting TOF mass spectrometer
• StepWave XS ion optics for improved ion transfer
• MassLynx v4.2 SCN1024 for acquisition; HDI v1.6 for image processing

Key Results and Discussion

Imaging data revealed clear localization of multiple phosphocholine lipids (e.g., PC 38:5 at m/z 808.59, PC 36:2 at m/z 788.62) and heme in the same tissue section. The SELECT SERIES MRT delivered mass resolving power exceeding 200,000 FWHM at m/z 200 and sub-ppm mass accuracy (RMS ~392 ppb). High resolving power allowed discrimination and co-localization of two lipids separated by only 81 mDa. Spatial resolution of 50 µm pixels and acquisition rate of 0.5 s/scan provided detailed molecular maps correlating with H&E histology.

Practical Benefits and Applications

High specificity and minimal sample preparation enable:

• Lipid profiling in neuroscience and biomarker discovery
• Drug distribution and metabolism studies in tissue sections
• Rapid screening in QA/QC for biopharmaceuticals
• Pathology research with molecular histology overlays

Future Trends and Opportunities

Ongoing advances may include integration with other imaging modalities (e.g., MALDI, optical microscopy) for multimodal analysis, real-time data encoding strategies to further boost throughput, and machine-learning-driven interpretation to handle the increasing data complexity in clinical and industrial settings.

Conclusion

The DESI XS source coupled to the SELECT SERIES MRT mass spectrometer delivers unprecedented combination of spatial resolution, mass resolving power, and accuracy for MSI applications. This platform significantly enhances confidence in molecular identification directly in tissue, opening new avenues for biological research and clinical diagnostics.