A gas-phase standard delivery system for direct breath analysis

Area of Science:

• Analytical Chemistry
• Biomedical Engineering
• Environmental Science

Background:

• Direct breath analysis using mass spectrometry (MS) is expanding, with secondary electrospray ionization coupled to high-resolution mass spectrometry (SESI-HRMS) emerging as a key technique.
• Current SESI-HRMS methods lack standardization for quality control and absolute quantification, hindering reliable clinical applications.
• The need for standardized protocols is critical for improving data accuracy and inter-laboratory comparability in breath analysis studies.

Purpose of the Study:

• To design and evaluate a custom standard delivery system for direct breath analysis using SESI-HRMS.
• To enable simultaneous introduction of multiple gas-phase standards in the parts-per-billion (ppb) to parts-per-million (ppm) range.
• To assess the system's performance in mimicking exhaled breath conditions (temperature and humidity) and its suitability for quality control and quantification.

Main Methods:

• Development of a custom-built standard delivery system capable of heating and humidifying gas flows to simulate exhaled breath.
• Introduction of single- and multi-component gas-phase standards into ambient MS setups (Orbitrap and QTOF).
• Inter-laboratory comparison and routine deployment over several weeks to evaluate stability, reproducibility, accuracy, precision, and sensitivity.

Main Results:

• The system demonstrated stable and reproducible performance with low between-run (<19%) and within-run (<20%) variations.
• High accuracy (96%-111%) and precision (>95%) were achieved for acetone quantification using single-compound standards.
• Compound-specific sensitivities were observed for multi-component standards, with limits of detection ranging from 0.05 ppb (1,8-cineol) to 3.1 ppb (p-xylene).

Conclusions:

• The developed standard delivery system significantly enhances data quality and comparability in direct breath analysis by SESI-HRMS.
• The system is suitable for reliable absolute quantification and monitoring instrument stability, crucial for longitudinal and multi-center studies.
• Routine use of this standardized system will advance the clinical application of breath analysis for disease diagnosis and monitoring.