Selected ion flow tube studies of the reactions of H30+, NO+ and O2+ with the anaesthetic gases halothane, isoflurane and sevoflurane

We have carried out a study of the reactions of H3O+, NO+ and O-2(+). the commonly used precursor ions for selected ion flow tube mass spectrometry (SIFT-MS), with three anaesthetic gases, halothane, isoflurane and sevoflurane. The motivation for this study was to provide the necessary kinetic data that would allow the quantification of these anaesthetic gases in operating theatre air and in the breath of theatre staff and post-operative patients. A clear negative result from these experiments is that NO+, although undergoing the simplest chemistry, is unsuitable for this SIFT-MS application. However, although the ion chemistry of H3O+ and O-2(+) with these compounds is very complex, there being several product ions in each reaction, many of which react rapidly with water molecules, monitor ions have been identified for all three anaesthetic gases when using H3O+ and O-2(+) as precursor ions. The detailed ion chemistry is discussed and the specific monitor ions are indicated. Hence, the feasibility of on-line breath monitoring is demonstrated by simple examples. These studies have opened the way to measurements in the clinical environment. Copyright (C) 2002 John Wiley Sons, Ltd.