Abstract
A major challenge for breath research is the lack of standardization in sampling and analysis. To address this, a test that utilizes a standardized intervention and a defined study protocol has been proposed to explore disparities in breath research across different analytical platforms and to provide benchmark values for comparison. Specifically, the Peppermint Experiment involves the targeted analysis in exhaled breath of volatile constituents of peppermint oil after ingestion of the encapsulated oil. Data from the Peppermint Experiment performed by proton transfer reaction mass spectrometry (PTR-MS) and selected ion flow tube mass spectrometry (SIFT-MS) are presented and discussed herein, including the product ions associated with the key peppermint volatiles, namely limonene, α- and β-pinene, 1,8-cineole, menthol, menthone and menthofuran. The breath washout profiles of these compounds from 65 individuals were collected, comprising datasets from five PTR-MS and two SIFT-MS instruments. The washout profiles of these volatiles were evaluated by comparing the log-fold change over time of the product ion intensities associated with each volatile. Benchmark values were calculated from the lower 95% confidence interval of the linear time-to-washout regression analysis for all datasets combined. Benchmark washout values from PTR-MS analysis were 353 min for the sum of monoterpenes and 1,8-cineole (identical product ions), 173 min for menthol, 330 min for menthofuran, and 218 min for menthone; from SIFT-MS analysis values were 228 min for the sum of monoterpenes, 281 min for the sum of monoterpenes and 1,8-cineole, and 370 min for menthone plus 1,8-cineole. Large inter- and intra-dataset variations were observed, whereby the latter suggests that biological variability plays a key role in how the compounds are absorbed, metabolized and excreted from the body via breath. This variability seems large compared to the influence of sampling and analytical procedures, but further investigations are recommended to clarify the effects of these factors.
Highlights
The detection of volatile organic compounds (VOCs) in exhaled breath offers a non-invasive approach to screen for and monitor health-related biomarkers [1,2,3]
A large spread was present within the washout profiles recorded for each dataset, as indicated by the high relative standard deviations (RSDs) in both proton transfer reaction mass spectrometry (PTR-MS) and selected ion flow tube mass spectrometry (SIFT-MS) results
The typical concentrations to measure are in the range of 1–25 ppbv, with some outliers reaching 50 ppbv. This technical note summarizes the data acquired by PTR-MS and SIFT-MS in the peppermint washout experiment
Summary
The detection of volatile organic compounds (VOCs) in exhaled breath offers a non-invasive approach to screen for and monitor health-related biomarkers [1,2,3]. There are various technologies for analysing exhaled breath, the most common being gas chromatography mass spectrometry (GC-MS), proton transfer reaction mass spectrometry (PTRMS), selected ion flow tube mass spectrometry (SIFTMS), ion mobility mass spectrometry (IMS) and laser-spectroscopy [1] This diverse nature of both sampling and analysis of breath volatiles poses a major challenge in comparing results from independent research groups. The proposed benchmarking study represents a straightforward tool for participating research institutions to compare multi-centre benchmark values against their own data to evaluate sampling and analysis proficiency This is achieved by measuring the relative changes in the breath concentrations of the volatiles contained within the peppermint oil capsule over time via breath, i.e. the washout. Technical papers on other techniques, including GC-MS, IMS, secondary electrospray ionization mass spectrometry and needle-trap micro-extraction with GC-MS analysis have been previously published [8,9,10] or are in the process of being published
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