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Reverse-Flow Engineering of a Liquid Microjunction Surface Sampling Probe for Ambient Ionization Mass Spectrometry
Mina Alidoust Sl1, Jian Yu1, Malek Hassan1
1Department of Chemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada.
Analytical Chemistry
|May 12, 2026
Summary
Reverse-flow engineering enhances liquid microjunction surface sampling probes (LMJ-SSP) by reducing clogging and improving stability. This method uses computational fluid dynamics and experiments for better mass spectrometric analysis of complex samples.
Area of Science:
- Analytical Chemistry
- Mass Spectrometry
- Surface Science
Background:
- Liquid microjunction surface sampling probe (LMJ-SSP) is vital for localized mass spectrometry.
- Limitations include low spatial resolution and particle-induced clogging.
- Optimizing flow dynamics is crucial for LMJ-SSP performance.
Purpose of the Study:
- To investigate the impact of flow direction on LMJ-SSP stability and clogging.
- To develop a reverse-flow configuration to overcome traditional design limitations.
- To enhance spatial resolution and reduce clogging propensity in LMJ-SSP.
Main Methods:
- Integration of computational fluid dynamics (CFD) modeling with experimental measurements.
- Systematic examination of flow direction effects on liquid microjunction stability, shear stress, and clogging.
- Application and testing of a reverse-flow configuration using fused-silica capillaries and annular gaps.
- Particle-tracking simulations and experimental clogging tests with microspheres and biological debris.
- Direct analysis of metabolites from complex biological samples (pollen, leaf tissues).
Main Results:
- CFD modeling showed a reorganized streamline, enhanced shear forces, and suppressed stagnation zones in reverse flow.
- Reverse flow created a more confined microjunction meniscus compared to normal flow.
- Experimental tests demonstrated a threefold reduction in clogging potential with reverse flow.
- Particle-tracking simulations confirmed outward radial trajectories preventing central blockage.
- Successful direct analysis of metabolites from particulate-rich plant tissues was achieved.
Conclusions:
- Reverse-flow engineering is a robust strategy for enhancing LMJ-SSP performance.
- This approach improves operational stability and reduces clogging.
- Consistent surface sampling from complex, particulate-rich samples is achievable under mass spectrometric conditions.
