Matrix Effects in Desorption Electrospray Ionization across Mineral and Rock Substrates

Area of Science:

• Geochemistry
• Analytical Chemistry
• Planetary Science

Background:

• Desorption electrospray ionization mass spectrometry imaging (DESI-MSI) is a powerful tool for in situ chemical analysis of geological and planetary materials.
• Quantitative DESI-MSI studies are often hindered by matrix effects, particularly those related to substrate properties.

Purpose of the Study:

• To systematically evaluate the impact of mineral and rock substrates on DESI-MSI signal response.
• To understand how substrate physical and chemical properties influence quantitative chemical imaging.

Main Methods:

• Investigated 25 mineral and rock substrates using DESI-MSI.
• Continuously infused a six-component internal-standard mixture into the spray solvent.
• Quantified ion responses across different substrates to assess matrix effects.

Main Results:

• Signal intensities decreased with increasing surface roughness, indicating physical sampling efficiency is critical.
• Different mineral classes showed systematic response variations even at similar roughness, influenced by crystal chemistry and interfacial effects.
• Substrates altered ion-form distributions (protonated/deprotonated species and adducts).

Conclusions:

• Substrate properties significantly influence DESI-MSI signal behavior, affecting ion yield and ion-form partitioning.
• Normalization using internal standards can mitigate substrate-driven variability in geological and planetary DESI-MSI.
• Findings provide a practical framework for improving quantitative accuracy in substrate-based DESI-MSI analyses.