New paradigm in ionization: multiply charged ion formation from a solid matrix without a laser or voltage.

Area of Science:

• Analytical Chemistry
• Mass Spectrometry
• Ionization Techniques

Background:

• Matrix-assisted laser desorption/ionization (MALDI) is a common technique for generating ions from solid samples.
• The precise mechanism of multiply charged ion formation in MALDI, particularly the role of the matrix, remains incompletely understood.

Purpose of the Study:

• To investigate alternative methods for producing multiply charged ions from solids using a heated inlet.
• To explore the fundamental requirements for ion formation, questioning the necessity of a laser in the ionization process.

Main Methods:

• Developed Laserspray Ionization (LSI) using laser ablation of matrix/analyte mixtures.
• Demonstrated alternative sample delivery methods, including using an air gun to propel pellets into a heated ionization zone.
• Analyzed protein samples using mass spectrometry under these conditions.

Main Results:

• Multiply charged protein ions were successfully produced using LSI and alternative delivery methods.
• Ionization was achieved solely by a heated inlet to the mass spectrometer, without electric fields or lasers.
• The matrix commonly used in MALDI proved effective under these simplified conditions.

Conclusions:

• The laser in LSI primarily serves to deliver sample to the ionization zone, not necessarily for direct ionization.
• Multiply charged ions can form under mild conditions with only a heated inlet, challenging established MALDI mechanisms.
• The importance of matrix structure and composition in ion formation warrants further investigation.