Morphology-Driven Control of Metabolite Selectivity Using Nanostructure-Initiator Mass Spectrometry

Area of Science:

• Analytical Chemistry
• Surface Science
• Mass Spectrometry

Background:

• Nanostructure-initiator mass spectrometry (NIMS) is a laser desorption/ionization technique.
• The technique relies on a nanostructure-trapped initiator phase.

Purpose of the Study:

• To investigate the relationship between NIMS surface morphology and analyte selectivity.
• To determine how surface characteristics influence NIMS sensitivity for diverse analytes.

Main Methods:

• Surface morphology was characterized using scanning electron microscopy and spectroscopic ellipsometry.
• NIMS sensitivity was assessed using mass spectrometry imaging on substrates with varying porosities.
• Anodic electrochemical etching was employed to generate NIMS substrates with controlled morphologies.

Main Results:

• NIMS surface porosity increased linearly with etching time, with pore sizes ranging from 4 to 12 nm.
• Small molecule (<2k Da) sensitivity increased with higher porosity.
• Large molecule sensitivity was highest on low-porosity, small-pore-size surfaces.

Conclusions:

• NIMS surface morphology significantly and selectively alters analytical sensitivity.
• Surface area restructuring likely drives small molecule signal enhancement with increased porosity.
• Strong interactions with initiator-coated pores may trap large molecules, reducing their signal on high-porosity surfaces.
• Designing NIMS surfaces with specific morphologies can enhance specificity for target molecules.