Rapid communications in mass spectrometry : RCM
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Rapid Commun. Mass Spectrom. · Jan 2000
Quantification of hydrogen sulphide in humid air by selected ion flow tube mass spectrometry.
We report the results of a study of the reactions of H(3)O(+), NO(+) and O(2)(+.) ions with H(2)S. This study was undertaken to provide a thorough understanding of the ion chemistry required for accurate quantification of H(2)S in humid air by selected ion flow tube mass spectrometry (SIFT-MS). It shows that slow reactions occur between H(3)S(+), the primary product ions of the H(3)O(+)/H(2)S reaction, and the abundant H(2)O molecules present in humid air and breath. ⋯ This study also shows that NO(+) does not react with H(2)S, and that O(2)(+.) does react rapidly with H(2)S, but the product H(2)S(+.) ions react rapidly with H(2)O. Thus, NO(+) and O(2)(+.) cannot be used as precursor ion for analysis of H(2)S in moist air by SIFT-MS. A sample SIFT mass spectrum is shown from which H(2)S and several other volatile compounds have been quantified in a sample of cow rumen gas.
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Rapid Commun. Mass Spectrom. · Jan 2000
Influence of water vapour on selected ion flow tube mass spectrometric analyses of trace gases in humid air and breath.
Selected ion flow tube mass spectrometry (SIFT-MS) detects and quantifies in real time the trace gases, M, in air/breath samples introduced directly into a flow tube. Inevitably, relatively large partial pressures of water vapour are introduced with the sample and the water molecules become involved in the ion chemistry on which this analytical technique depends. When H(3)O(+) ions are used as the precursors for chemical ionisation and SIFT mass spectrometric analyses of M, they generally result in the formation of MH(+) ions. ⋯ Additionally, some fundamental data have been obtained on the association reactions of protonated organic molecules, MH(+) ions, with water molecules forming MH(+). H(2)O monohydrate ions. For some types of M, reaction sequences occur that lead to the formation of dihydrate and trihydrate ions.