Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry using an inorganic particle matrix for...

Area of Science:

• Analytical Chemistry
• Materials Science

Background:

• Conventional organic matrices in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) can present limitations.
• Exploring inorganic matrices, specifically fine metal or metal oxide powders, offers an alternative for analyzing low molecular mass analytes.

Purpose of the Study:

• To evaluate eleven types of metal and metal oxide powders as matrices for MALDI-TOFMS.
• To identify an optimal inorganic matrix for the analysis of poly(ethylene glycol) 200 (PEG 200) and methyl stearate.

Main Methods:

• Eleven inorganic powders (Al, Mn, Mo, Si, Sn, SnO2, TiO2, W, WO3, Zn, ZnO) were tested as matrices.
• Analytes were mixed with the inorganic powder and a liquid dispersant, then analyzed using a 337 nm pulsed nitrogen laser MALDI-TOFMS instrument.
• Performance was assessed based on analyte ionization, spectral intensity, and background noise.

Main Results:

• Most inorganic matrices successfully ionized analytes as alkali metal adducted ions ([M+Na]+ or [M+K]+) or protonated molecules ([M+H]+).
• SnO2 was ineffective as a matrix for the tested analytes.
• TiO2, when suspended in liquid paraffin, produced spectra with the lowest background noise and highest intensity for both PEG 200 and methyl stearate.

Conclusions:

• Metal and metal oxide powders, particularly TiO2, are viable and effective matrices for MALDI-TOFMS analysis of small molecules.
• The rapid heating and vaporization of bulk particles under laser irradiation facilitate analyte ionization.
• This method provides a robust approach for obtaining low-background mass spectra of small compounds.