Benchmarking breath analysis using peppermint approach with gas chromatography ion mobility spectrometer coupled to micro thermal desorber.

Background
The Peppermint Initiative, established within the International Association of Breath Research, introduced the peppermint protocol, a breath analysis benchmarking effort designed to address the lack of inter-comparability of outcomes across different breath sampling techniques and analytical platforms. Benchmarking with gas chromatography - ion mobility spectrometry (GC-IMS) using peppermint has been previously reported however, coupling micro-thermal desorption (µTD) to GC-IMS has not yet, been benchmarked for breath analysis.
Objective
To benchmark µTD-GC-IMS for breath analysis using the peppermint protocol.
Methods 
Ten healthy participants (4 males and 6 females, aged 20 - 73 years), were enrolled to give six breath samples into Nalophan bags via a modified peppermint protocol. Breath sampling after peppermint ingestion occurred over 6 h at t = 60, 120, 200, 280, and 360 minutes. The breath samples (120 cm3) were pre-concentrated in the µTD before being transferred into the GC-IMS for detection. Data was processed using VOCal, including background subtractions, peak volume measurements, and room air assessment. 
Results
During peppermint washout, eucalyptol showed the highest change in concentration levels, followed by α-pinene and β-pinene. The reproducibility of the technique for breath analysis was demonstrated by constructing logarithmic washout curves, with the average linearity coefficient of R2 = 0.99. The time to baseline (benchmark) value for the eucalyptol washout was 1111 minutes (95% CI: 529-1693 minutes), obtained by extrapolating the average logarithmic washout curve. 
Conclusion
Using the peppermint protocol, we demonstrated that µTD-GC-IMS is reproducible and suitable for breath analysis. We obtained a benchmark value (eucalyptol washout) for the µTD-GC-IMS of 1111 minutes (95% CI: 529-1693 minutes) for eucalyptol, which is comparable to the gold standard GC-MS. &#xD.