High-resolution mass spectrometry exhalome profiling with a modified direct analysis in real time ion source

Area of Science:

• Analytical Chemistry
• Metabolomics
• Biomedical Science

Background:

• Exhaled breath composition reflects human metabolism.
• Analyzing breath metabolites is vital for health but technically challenging due to volatile, low-level compounds.
• Challenges include instantaneous diffusion, modification, and low concentrations of volatile molecules.

Purpose of the Study:

• To develop and validate a direct analysis method for human breath metabolites.
• To enable rapid and efficient identification and quantification of exhaled volatile organic compounds.
• To provide a more complete picture of the human breath metabolome.

Main Methods:

• Utilized a modified direct analysis in real-time ion source coupled with high-resolution mass spectrometry (Orbitrap).
• Employed both online monitoring and offline analysis in positive and negative ion modes.
• Developed an improved system for direct sampling, rapid transmission, and efficient ionization of breath volatiles and condensates.

Main Results:

• Demonstrated distinct molecular features between online and offline breath analysis.
• Identified approximately 65 metabolites in positive ion mode and 55 in negative ion mode using accurate m/z values.
• Obtained exhalome profiles, compound class proportions, and observed daily variations in metabolite content.

Conclusions:

• Combined online and offline analysis provides a comprehensive human breath metabolome.
• The developed method offers rapid, direct analysis of breath samples with minimal sample preparation.
• Features include simple operation and straightforward metabolite identification for diverse sample statuses.