MALDI Mass Spectrometry of Small Molecules Using Nanometer-sized Clay

Area of Science:

• Analytical Chemistry
• Materials Science
• Nanotechnology

Background:

• Matrix-assisted laser desorption ionization mass spectrometry (MALDI MS) is a crucial technique for analyzing diverse molecules.
• Allophane, a nanometer-sized clay, presents unique properties for potential use as a MALDI MS matrix.

Purpose of the Study:

• To investigate allophane as a matrix for MALDI MS, focusing on small molecules and high molecular weight compounds.
• To explore the influence of alkali-cation exchange on allophane's ionization efficiency.
• To evaluate the synergistic effects of combining allophane with zeolite for enhanced ionization.

Main Methods:

• Utilized cation-exchanged allophane as a matrix in MALDI MS.
• Analyzed small molecules (fructose) and high molecular weight compounds (cyclodextrin, angiotensin II, insulin).
• Investigated the combination of allophane and zeolite for proton relay-assisted ionization.

Main Results:

• Cation exchange on allophane proceeded smoothly, influenced by alkali metal atomic number and counter anion size.
• Analyte peak intensity of fructose decreased with increasing alkali metal atomic number, explained by cation stability, desorption energy, and solvation enthalpy.
• Allophane demonstrated applicability for high molecular weight compounds.
• Combining allophane with zeolite enhanced the ionization of 1,8-bis(dimethylamino)naphthalene by 2.2 times through proton relay.

Conclusions:

• Allophane is a versatile matrix for MALDI MS, effective for both small and large molecules.
• Alkali-cation properties significantly impact ionization efficiency, offering tunable matrix characteristics.
• The allophane-zeolite combination shows promise for enhanced ionization via proton relay mechanisms.