Direct Analysis of Fatty Acid Vapors in Breath by Electrospray Ionization and Atmospheric Pressure Ionization-Mass Spectrometry

• Published in: Analytical chemistry (Washington) 2008-11, Vol.80 (21), p.8210-8215
• Main Authors: Martínez-Lozano, Pablo, Fernández de la Mora, Juan
• Format: Article
• Language: English
• Subjects: Aldehydes; Analytical chemistry; Atmospheric Pressure; Breath Tests; Fatty acids; Fatty Acids - analysis; Fatty Acids - chemistry; Humans; Ion Channels - chemistry; Mass spectrometry; Online Systems; Probability; Spectrometry, Mass, Electrospray Ionization - methods; Volatilization
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac801185e

Real time analysis of human breath is achieved in an atmospheric pressure ionization mass spectrometer (API-MS) by negatively charging exhaled vapors via contact with an electrospray cloud. The spectrum observed is dominated by a wide range of deprotonated fatty acids, including saturated chains up to C14. Above C14, the background from cutaneous sources becomes dominant. We also tentatively identify a series of unsaturated fatty acids (C7−C10), ketomonocarboxylic acids (C6−C10), and a family of aldehydes. The ionization probability of large fatty acids increases drastically when the humidity changes from 20% to 95%. Accordingly, distinguishing lung vapors (humid) from those in the background (dry) requires special precautions. Estimated fatty acid vapor concentrations in breath based on our measurements (∼100 ppt) are in fair agreement with values expected from blood concentrations in the range for which data are available (C3−C6).