Improving Molecular-Level Understanding of Atmospheric Oxygenated Organic Molecules Using Online High-Resolution...

Area of Science:

• Atmospheric Chemistry
• Aerosol Science
• Analytical Chemistry

Background:

• Atmospheric oxygenated organic molecules (OOMs) are critical for secondary organic aerosol (SOA) formation and new particle growth.
• Current mass spectrometry techniques lack the resolution for comprehensive molecular-level characterization of OOMs.
• Accurate identification of OOMs is essential for understanding atmospheric processes and air quality.

Purpose of the Study:

• To develop and evaluate a high-resolution nitrate chemical-ionization Orbitrap mass spectrometer (NO3-Orbitrap) for OOM analysis.
• To compare the performance of the NO3-Orbitrap with a conventional nitrate chemical-ionization time-of-flight mass spectrometer (NO3-TOF).
• To introduce a new framework for improving OOM identification in existing NO3-TOF datasets.

Main Methods:

• Development of a high-resolution NO3-Orbitrap MS.
• Parallel field and laboratory intercomparison between NO3-Orbitrap and NO3-TOF.
• Development of a modified spectral fitting framework (NO3-TOF_Modified) based on Orbitrap data.

Main Results:

• The NO3-Orbitrap successfully resolved complex OOMs with high mass accuracy (<0.01 Da).
• The NO3-Orbitrap identified significantly more OOM peaks than the NO3-TOF, revealing substantial misidentification in TOF data.
• The NO3-TOF_Modified framework reduced peak misidentification and increased agreement between instruments, though concentration differences persisted due to resolution and sensitivity limitations.

Conclusions:

• Ultrahigh-resolution mass spectrometry is essential for accurately characterizing the complexity of atmospheric OOMs.
• The developed NO3-TOF_Modified framework enhances OOM identification in both current and historical datasets.
• Further advancements are needed to fully resolve OOMs and their contribution to atmospheric processes.