Enhanced Signal Intensity via Rapid Suspension-Based Analyte Deposition on Titanium Foils for Laser-Induced Acoustic Desorption-Mass Spectrometry Experiments

Laser-induced acoustic desorption (LIAD) has emerged as a promising sample evaporation technique for analytical applications, including mass spectrometry (MS) and molecular rotational resonance (MRR) spectroscopy. The method involves depositing solid samples onto the front side of a thin Ti foil and irradiating the back side with high-energy laser pulses, causing desorption of neutral low-energy gas-phase molecules. However, conventional solution-based sample deposition methods are limited by analyte-solvent compatibility. Furthermore, the desorption efficiency is not always as high as desired. To overcome these limitations, a modified deposition method based on ultrasonic spraying of analyte suspensions onto Ti foils was developed. Model compounds of different sizes and types were deposited using both the conventional and new approach. Foils were characterized by using optical microscopy to assess analyte morphology and crystal size. The suspension-based method enabled faster analyte deposition, broader solvent compatibility, more homogeneous coatings, and smaller analyte crystals. The foils were then subjected to LIAD in a linear quadrupole ion trap mass spectrometer equipped with an atmospheric pressure chemical ionization source. LIAD MS analysis demonstrated improved signal stability and intensity for most compounds deposited from suspensions, together with a sample amount-dependent response that was not found for measurements involving the traditional sample deposition methods.