Direct analysis of fatty acid vapors in breath by electrospray ionization and atmospheric pressure ionization-mass spectrometry.
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 ( approximately 100 ppt) are in fair agreement with values expected from blood concentrations in the range for which data are available (C3-C6).
Martínez-Lozano
Pablo
P
SEADM, Parque Tecnologico de Boecillo, Valladolid, Spain 47151.
Fernández de la Mora
Juan
J
D001274:Atmospheric Pressure; D001944:Breath Tests; D005227:Fatty Acids / Q000032:analysis* / Q000737:chemistry*; D006801:Humans; D007473:Ion Channels / Q000737:chemistry; D009862:Online Systems; D011336:Probability; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D014835:Volatilization
D005227:Fatty Acids; D007473:Ion Channels