Monitoring Trace VOCs in Human Breath Emissions with PTR-MS

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The ultra-low limits of detection of the Vocus PTR-TOF mass spectrometer enable the monitoring of sub-second changes in human breath VOC emissions, ranging from ppt to ppm concentration.

Luca Cappellin and Felipe Lopez
TOFWERK, Thun, Switzerland

Researchers in many fields must characterize the emission and evolution of target VOCs during fast biological, chemical or industrial processes.  Such measurements require online monitoring methods with large dynamic range and high time resolution.   Proton Transfer Reaction Mass Spectrometry (PTR-MS) is an ultra-sensitive technique for real-time detection of diverse volatile organic compounds (VOCs).  

The Vocus PTR-TOF is able to simultaneously measure large numbers of VOCs with ultra-low limits of detection, fast time response, and high mass resolving power.   To demonstrate its ability to monitor dynamic changes in a complex VOC mixture, human breath was directly measured throughout the ingestion of a RicolaTM herb cough drop.  The 13 herbs in these cough drops each have their own aroma compounds at concentrations spanning many orders of magnitude.

The figure below shows the evolution of select VOCs during the consumption of the cough drop.  High resolution PTR-MS data were saved at a rate of 3 mass spectra/sec to capture rapid changes in VOCs related to herb aroma and metabolism. 1 pptv fluctuations of menthyl acetate were captured at sub-second resolution.   Simultaneously, the instrument captured rapid changes in C10H16 monoterpenes, which had concentrations that were 5 to 6 orders of magnitude greater than menthyl acetate.

Real-time monitoring of VOCs in human breath throughout the consumption of a RicolaTM herb cough drop. Human breath was directly sampled into the inlet of a Vocus PTR-TOF 2R before and after ingestion of the cough drop. High-resolution data were saved at a rate of 3 mass spectra/sec to capture rapid and large-magnitude changes in both herb aroma VOCs, terpenes and esters, and VOCs related to the human metabolism, such as isoprene, with sub-second resolution. Concentrations of the monitored species spanned more than 6 orders of magnitude during the experiment (ppt to ppm).