Journal of breath research
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We have carried out a selected ion flow tube mass spectrometry (SIFT-MS) study of the concentrations of the sulfur-containing compounds H(2)S (using H(3)O(+) precursor ions), CH(3)SH (H(3)O(+)), (CH(3))(2)S (O(2)(+)), (CH(3))(2)S(2) (NO(+)) and CS(2) (O(2)(+)) in single exhalations of mouth-exhaled breath and nose-exhaled breath and in the static gas in the oral cavity for two healthy volunteers. The primary purpose of the study was to show how compounds present in breath at levels as low as a part per billion (ppb) can be identified and quantified if the overlap of 'impurity' isobaric ions with the analytical product ions for each trace compound is identified and accounted for. The H(2)S measurements are straightforward using H(3)O(+) precursor ions, since no overlapping ions are recognized and its breath concentration is relatively high at typically 20-70 ppb. ⋯ It was not possible to quantify CS(2) in the breath because of serious interference (overlapping ions) due to the presence of carbon dioxide and acetone that inevitably occur in exhaled breath. This study paves the way for the accurate analysis of these sulfur compounds in halitosis and potentially for probing the diseased state, especially liver disease, by breath analysis. To demonstrate the simplicity of measuring these compounds when they are present at levels of about 100 ppb and greater, data are presented on the emissions of these sulfur-containing compounds from Pseudomonas bacterial cultures in vitro.
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The sensitivity of selected ion flow tube mass spectrometry, SIFT-MS, has been increased such that it is now possible to detect metabolites present at a part-per-billion, ppb, level in single breath exhalations. However, to utilize this improved sensitivity, the overlaps (coincidences) of those ions resulting from interfering reactions of impurity precursor ions with some breath metabolites present at higher concentrations with the analytical product ions characteristic of particular metabolites must be accounted for. ⋯ It is shown that when using H(3)O(+) to quantify formaldehyde and acetaldehyde the reactions of impurity O(2)(+) ions with methanol and ethanol (always present in breath) must be accounted for and that the quantification of acetaldehyde must avoid the interference of the CO(2) present in exhaled breath. Finally, it is indicated that the analysis of 2-propanol can be achieved using both H(3)O(+) and NO(+) precursor ions.