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

Abstract

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.