Selective monitoring of breath isoprene by a portable detector during exercise and at rest

Abstract

Isoprene has received widespread attention in breath research because of its potential to serve as a sensitive and non-invasive biomarker for the detection and monitoring of several metabolic effects. To date, research activity on breath isoprene focused on mass spectrometry-based measurement techniques, which are not portable and require skilled operators. Here, we show, for the first time to our knowledge, selective isoprene monitoring in exhaled breath (148 breath samples, 60–1250 parts-per-billion, ppb) with an inexpensive, user-friendly and compact filter–sensor device. This detector is based on a previously developed concept comprising a sorption filter of activated alumina that removes hydrophilic volatiles ahead of a micro gas sensor consisting of chemoresistive Si-doped WO3 nanoparticles to quantify the isoprene down to few ppb concentrations. When tested on humans during exercise and at rest, the detector accurately followed breath isoprene dynamics in linear (Pearson’s coefficient 0.89) correlation to proton transfer reaction mass spectrometry measurements. Most importantly, the output from the device is not interfered by high and variable concentrations of other breath volatile compounds, specifically acetone, ethanol and methanol. This isoprene detector can be readily applied for online monitoring of physical activity.