Article ID Journal Published Year Pages File Type
1192846 International Journal of Mass Spectrometry 2012 10 Pages PDF
Abstract

Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) is a very useful tool for high frequency detection and quantification of gas-phase volatile organic compounds (VOCs) but the soft ionization means it is difficult to discriminate structural isomers. For example, to date it has only been possible to measure the sum of monoterpene concentrations, which have been monitored most commonly at m/z 81 and 137 at a constant drift voltage and pressure. We show here that PTR-MS is capable of discriminating individual monoterpenes when operating in the alternating drift voltage (AD) mode. The approach is based on the principle that slightly different energies are required for the fragmentation/clustering of a given monoterpene, so in AD mode each monoterpene has different time points for fragmentation. Therefore from a fragmentation analysis of background-subtracted standards it is possible to calculate the percentage of each monoterpene in an absolute concentration of their sum. Although monoterpenes have been chosen as an example, the method is likely to be effective for other structural isomeric species such as the sesquiterpenes or methyl vinyl ketone/methacrolein (MVK/MACR).

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (220 K)Download as PowerPoint slideHighlights► An alternating drift voltage (AD) mode expands the analytical capabilities of PTR-MS. ► Discrimination of structural isomers is possible with a PTR-MS running in AD mode. ► Different drift energies yield variation in isomer fragmentation/clustering. ► Ratios of m/z 81–137 in the AD mode characterise monoterpenes in the ppb range. ► The method is likely to be effective for other structural isomeric species.

Related Topics
Physical Sciences and Engineering Chemistry Analytical Chemistry
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