Challenges in the identification and quantitation in on-line breath analysis

Area of Science:

• Analytical Chemistry
• Biomedical Diagnostics

Background:

• Volatile organic compounds (VOCs) in exhaled breath hold diagnostic potential.
• Secondary electrospray ionization-mass spectrometry (SESI-MS) detects thousands of VOCs.
• MS1 measurements in SESI-MS are prone to identification errors.

Purpose of the Study:

• To evaluate SESI-MS acquisition methods for VOC identification and quantification in human breath.
• To assess the utility of MS2 measurements for targeted compounds.

Main Methods:

• Analyzed endogenous breath compounds (aldehydes, limonene, pyridine) in 12 volunteers.
• Employed full scan, selected ion monitoring, and parallel reaction monitoring acquisition methods.
• Validated identifications and quantifications against external standards and MS2 data.

Main Results:

• Limonene and pyridine were successfully identified and quantified using all methods, with MS2 support.
• MS2 data showed limitations in separating limonene from pinenes.
• Low-abundance aldehydes were difficult to distinguish from isomeric ketones, leading to false assignments and inaccurate quantification.

Conclusions:

• While SESI-MS with MS2 enhances VOC analysis in breath, challenges remain for low-abundance and isomeric compounds.
• Careful method selection and validation are crucial for reliable breath biomarker discovery.