Selected-ion flow-tube mass spectrometry (SIFT-MS) has been used to monitor the volatile compounds in the exhaled breath of 30 volunteers (19 male, 11 female) over a 6-month period. Volunteers provided breath samples each week between 8:45 and 13:00 (before lunch), and the concentrations of several trace compounds were obtained. In this paper the focus is on ethanol and acetaldehyde, which were simultaneously quantified by SIFT-MS using H3O+ precursor ions. The mean ethanol level for all samples was 196 parts-per-billion (ppb) with a standard deviation of 244 ppb, and the range of values for breath samples analysed is 0 to 1663 ppb. The mean acetaldehyde level for all samples was 24 ppb with a standard deviation of 17 ppb, and the range of values for breath samples analysed is 0 to 104 ppb. Background (ambient air) levels of ethanol were around 50 ppb, whereas any background acetaldehyde was usually undetectable. Increased ethanol levels were observed if sweet drink/food had been consumed within the 2 h prior to providing the breath samples, but no increase was apparent when alcohol had been consumed the previous evening. The measured endogenous breath ethanol and acetaldehyde levels were not correlated. These data relating to healthy individuals are a prelude to using breath analysis for clinical diagnosis, for example, the recognition of bacterial overload in the gut (ethanol) or the possibly of detecting tumours in the body (acetaldehyde).
(c) 2005 John Wiley & Sons, Ltd.