Infrared matrix-assisted laser desorption and ionization by using a tunable mid-infrared free-electron laser

Area of Science:

• Analytical Chemistry
• Mass Spectrometry
• Spectroscopy

Background:

• Infrared matrix-assisted laser desorption/ionization (IR-MALDI) is a mass spectrometry technique.
• Conventional IR-MALDI utilizes fixed-frequency infrared lasers.
• Selective vibrational excitation is key to IR-MALDI's mechanism.

Purpose of the Study:

• To report initial results of IR-MALDI using a free-electron laser.
• To demonstrate IR-MALDI's capability with selective vibrational excitation.
• To explore IR-MALDI at wavelengths beyond conventional fixed-frequency lasers.

Main Methods:

• Utilized the Vanderbilt free-electron laser for selective vibrational excitation.
• Performed IR-MALDI mass spectrometry in the 2.8–4 µm and 5.5–6.5 µm wavelength ranges.
• Analyzed organic compounds like succinic acid, fumaric acid, and nicotinic acid as matrices.

Main Results:

• Demonstrated successful IR-MALDI of proteins using a tunable free-electron laser.
• Showed feasibility and comparable performance of IR-MALDI at new wavelengths.
• Obtained IR-MALDI mass spectra covering O-H and C=O stretch vibration absorption bands.

Conclusions:

• IR-MALDI is feasible and effective using tunable laser sources beyond conventional fixed frequencies.
• The study highlights the potential of IR-MALDI near C=O stretch vibrations.
• Tunable sources offer new avenues for studying IR-MALDI mechanisms.