Breath analysis using online mass spectrometry is proving to be a valuable tool for identifying prospective disease biomarkers and tracking the disease evolution and progression of therapeutic therapy. The uptake of molecules from inhaled air into the lungs may also be measured via mass spectral breath analysis.
Volatility, solubility and polarity all play a role in uptake, with certain substances flowing through the blood-air barrier more easily than others for distribution throughout the body. For risk assessment linked to short- or long-term exposure, accurate calculation of a potentially hazardous compound’s absorption is important.
Image Credit: TOFWERK
Figure 1 depicts the continuous measurement of inhaled and exhaled air for a participant in an indoor laboratory area using a Vocus 2R PTR-TOF and a dedicated breath inlet. On a log scale, the concentrations of acetone, isoprene, and N-methyl-2-pyrrolidone are displayed with time. As evidenced by the increasing amount during exhalation, acetone and isoprene are frequent components in both ambient air and human exhalation.
N-methyl-2-pyrrolidone is a pollutant that comes from the laboratory flooring and is found in the room air at a concentration of around 70 pptv. N-methyl-2-pyrrolidone is constantly less plentiful in exhaled air than in inhaled room air, in contrast to acetone and isoprene. This reduction suggests that following inhalation, the compound is taken up in the lungs.
By integrating Vocus data with spirometric data, the net uptake of N-methyl-2-pyrrolidone may be calculated. This is accomplished by multiplying the difference between the compound’s ambient and breath concentrations by the airflow from the lungs, as follows:
Where t1 and t2 are the start and end times of the recorded breath exhalation, respectively; C(t) is the compound concentration determined by Vocus during the exhalation; Clab is the compound’s laboratory concentration; f(t) is the exhalation airflow. The absorption of N-methyl-2-pyrrolidone into the lungs is estimated to be 0.3 ng/breath using this method.
Figure 1. Analysis of human breath at 5 Hz by a TOFWERK Vocus 2R PTR-TOF over a period of 10 minutes. The subject inhales air from the laboratory and exhales into the breath inlet of the instrument. The time evolution of acetone (blue), isoprene (green) and N-methyl-2-pyrrolidone (red) are reported. The latter is an air contaminant originating from the laminate used in the laboratory flooring and is always present. In these data, its concentration is consistently higher in the inhaled air and lower in the exhaled air, indicating uptake of the compound in the lungs. Image Credit: TOFWERK
TOFWERK is a global leader in time-of-flight mass spectrometry, delivering sensitive instruments for laboratory, industrial, and field analyses. Our customers’ interests range from materials science and geochemistry to metabolomics and trace-gas
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Our end-user product line includes the icpTOF, Vocus PTR-TOF, IMS-TOF, and EI-TOF for GC. These mass spectrometers bring the speed and sensitivity of TOFMS to many disciplines and sample types.
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