Detection of acetone and isoprene in human breath using a combination of thermal desorption and selected ion flow tube mass spectrometry

The measurement of volatile chemicals in human exhalant (breath analysis) has recently emerged as a non-invasive technique with the potential for the early diagnosis of disease. A common method of volatile chemical collection is to capture gases onto a solid phase sorbent followed, at a later time, by thermal release and analysis. This technique, termed thermal desorption (TD), may be a useful means to collect and store breath volatiles in a clinical setting prior to analysis. TD is, however, normally used in conjunction with gas chromatography (TD-GC) which results in slow analysis times and the required use of chemical standards. The new technique of selected ion flow tube mass spectrometry (SIFT-MS) offers a more rapid analysis process without the need for standards. SIFT-MS is normally used to analyze gas concentration in real-time and it is unclear whether combined TD and SIFT-MS can be successfully employed for breath analysis. We found that there was an approximate 1 to 1 concordance between levels of isoprene or acetone in the breath of 12 healthy volunteers measured either using real-time SIFT-MS or offline using a combination of SIFT-MS and TD (TD-SIFT-MS). The use of higher volumes of human breath did impact TD-SIFT-MS measurements of isoprene (but not acetone) with an apparent ceiling effect being observed. Nevertheless our findings demonstrate the potential for breath analysis using a combination of TD and SIFT-MS, an approach which may find utility in a clinical setting which does not allow online analysis of breath.