Breath Analysis with a (Very) Fine Toothed Comb

GC-MS is the most widely used analytical technique in breath analysis. But a relatively slow technique that can usually only detect one chemical at a time is impractical for real-world testing. That’s why a group of researchers decided to tackle the problem by using mid-infrared cavity-enhanced direct-frequency comb spectroscopy (CE-DFCS) to simultaneously detect and monitor four health biomarkers – methanol, methane, water and a form of heavy water (HDO) – in the breath of a volunteer (1).

The novel system “fingerprints” chemicals by measuring the amount of light absorbed as a laser frequency comb passes back and forth through breath samples loaded into a mirrored glass tube. Recent upgrades include a shift in the light spectrum analyzed from the near-infrared to the mid-infrared band and advances in optical coatings, both of which have allowed detection sensitivity up to the parts-per-trillion level – a thousandfold improvement.

The researchers are confident that, by extending the comb lasers further into the infrared, they’ll be able to identify many hundreds of trace breath chemicals at once (2).

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