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Title: CF3(+) and CF2H(+): new reagents for n-alkane determination in chemical ionisation reaction mass spectrometry.
Authors: Blake, Robert S.
Ouheda, Saleh A.
Evans, Corey J.
Monks, Paul S.
First Published: 10-Nov-2016
Publisher: Royal Society of Chemistry
Citation: Analyst, 2016, 141 (24), pp. 6564-6570
Abstract: Alkanes provide a particular analytical challenge to commonly used chemical ionisation methods such as proton-transfer from water owing to their basicity. It is demonstrated that the fluorocarbon ions CF3(+) and CF2H(+), generated from CF4, as reagents provide an effective means of detecting light n-alkanes in the range C2-C6 using direct chemical ionisation mass spectrometry. The present work assesses the applicability of the reagents in Chemical Ionisation Mass Spectrometric (CI-TOF-MS) environments with factors such as high moisture content, operating pressures of 1-10 Torr, accelerating electric fields (E/N) and long-lived intermediate complex formation. Of the commonly used chemical ionisation reagents, H3O(+) and NO(+) only react with hexane and higher while O2(+) reacts with all the target samples, but creates significant fragmentation. By contrast, CF3(+) and CF2H(+) acting together were found to produce little or no fragmentation. In dry conditions with E/N = 100 Td or higher the relative intensity of CF2H(+) to CF3(+) was mostly less than 1% but always less than 3%, making CF3(+) the main reagent ion. Using O2(+) in a parallel series of experiments, a substantially greater degree of fragmentation was observed. The detection sensitivities of the alkanes with CF3(+) and CF2H(+), while relatively low, were found to be better than those observed with O2(+). Experiments using alkane mixtures in the ppm range have shown the ionisation technique based on CF3(+) and CF2H(+) to be particularly useful for measurements of alkane/air mixtures found in polluted environments. As a demonstration of the technique's effectiveness in complex mixtures, the detection of n-alkanes in a smoker's breath is demonstrated.
DOI Link: 10.1039/c6an02118b
ISSN: 0003-2654
eISSN: 1364-5528
Version: Post-print
Status: Peer-reviewed
Type: Journal Article
Rights: Creative Commons “Attribution Non-Commercial No Derivatives” licence CC BY-NC-ND, further details of which can be found via the following link: Archived with reference to SHERPA/RoMEO and publisher website.
Description: Electronic supplementary information (ESI) available. See DOI: 10.1039/c6an02118b
Appears in Collections:Published Articles, Dept. of Chemistry

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