AS211: Real-Time Speciation of Ethylbenzene from the Xylenes Using SIFT-MS

Martin Perkins

11th September 2019

Ethylbenzene and the Xylenes are part of a group of compounds known as BTEX (benzene, toluene and xylenes). These compounds originate in the environment from a number of sources. They may present a potential human health risk, in particular from inhalation. As a result, they are included in environmental and occupational monitoring programs. Regulations are increasingly calling for separated measurements from BTEX analysis due to different occupational exposure limits.

Previously this would have required chromatographic separation of the isomers using specific gas chromatography methods. These methods need static samples taken at different time points, rather than performing analysis in real-time. Direct Mass Spectrometry (DMS) techniques traditionally have also struggled to distinguish ethylbenzene from the xylene isomers. As a result, measurement has been reported as a total concentration of “ethylbenzene plus xylenes”.

By contrast, Selected Ion Flow Tube Mass Spectrometry (SIFT-MS) is able to readily achieve direct, realtime speciation of the xylenes from ethylbenzene. This offers a whole raft of benefits. Especially given the ever increasing industry need for rapid speciation — whether in the lab, or in-process.

Clearly, higher resolution MS is not a solution, because the elemental composition is the same. Therefore, utilising an ionization approach that yield different products is required. With a portfolio of eight rapidly switchable reagent ions, Selected Ion Flow Tube Mass Spectrometry (SIFT-MS – from Syft Technologies) is the ideal technique with which to seek a real-time solution to problem.

This application note describes a ground-breaking approach to resolving the ethylbenzene from the xylene isomers using different reactivities with the O2+ reagent ion of SIFT-MS. Based on calibration, it enables the SIFT-MS technique to achieve direct, realtime speciation of the xylenes from ethylbenzene for the most most effective real-time BTEX analysis possible.



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