Strategies for Minimizing Interference from Metastable Water Clusters in ToF-SIMS 3D Imaging of Frozen Hydrated...

Area of Science:

• Mass Spectrometry
• Analytical Chemistry
• Biophysics

Background:

• Cryogenic analysis of hydrated biological samples is essential for preserving native structures during time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging.
• Water cluster ions from ice cause spectral interferences, hindering analyte detection and leading to mass peak misassignments in ToF-SIMS.

Purpose of the Study:

• Investigate the water ice spectrum within a specific ToF mass analyzer.
• Understand and mitigate spectral interferences caused by water cluster ions in ToF-SIMS.
• Optimize ToF-SIMS analysis of cryogenic frozen hydrated biological samples.

Main Methods:

• Utilized a gridless multistage reflectron ToF mass analyzer with dual acceleration zones.
• Analyzed the water ice spectrum of a cryogenic frozen hydrated organic solution.
• Investigated the influence of analyzer settings on metastable water cluster ion peaks.

Main Results:

• Identified distinct metastable peaks from single and multiple water molecule losses in different drift zones.
• Determined that analyzer settings influence metastable peak positions and origins.
• Confirmed that background signals primarily stem from pure ((H2O)nH+) and cationized ((H2O)nR+) water clusters.
• Observed single H2O loss peaks between 200-415 m/z and multiple H2O loss peaks above 415 m/z.

Conclusions:

• Developed strategies to minimize spectral interference from metastable water cluster ions.
• The study provides a foundation for improved analyte detection in ToF-SIMS of hydrated biological samples.
• Understanding water cluster ion behavior is key to accurate mass spectrometry analysis of frozen samples.