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Advantages of High Mass Resolution PTR-TOFMS
Chocolate...delicious for humans, challenging for analytical methods, perfect for demonstrating the benefits of high mass resolution PTR-TOFMS!
The real-time, direct injection PTR technology combined with powerful TOF-MS enables rapid, highly selective and quantitative screening of food, flavor and fragrance samples.
When High Mass-Resolution Gives the Competitive Edge
Recently, IONICON performed an extensive food and flavor study comparing their ultimate-resolution trace VOC analyzer PTR-TOF 10k to a common high-resolution PTR-TOFMS instrument. While the PTR-TOF 10k is equipped with the ioniTOF 10k platform which enables mass resolutions of 10,000 – 15,000 m/Δm, the comparison device was tuned to more common 5,000 m/Δm. The aim of the study was to identify the main advantages of exceptionally high mass resolution for food and flavor science.
Probably the most impressive example of the superiority of the PTR-TOF 10k was found during the analysis of the complex headspace of chocolate for the presence of ethyl maltol (C7H8O3.H+, m/z 141.055). With 5,000 m/Δm mass resolution at nominal m/z 141 the presence of five mass peaks is indicated (grey line). Interestingly, at about m/z 141.05 there appears to be rather a dip than a peak. By looking at the PTR-TOF 10k data (blue line) acquired from the same sample, the situation gets immediately unambiguous. Ethyl maltol is clearly present (orange area) and fully separable from other isobars in the chocolate headspace. However, its intensity is about an order of magnitude lower than those of the most abundant isobar and thus, ethyl maltol is virtually undetectable with 5,000 m/Δm.
Similar results have been found for many other m/z, e.g. for nominal m/z 153, which is shared by the isobaric aroma compounds vanillin, ethylguaiacol and carveol. Again, only the PTR-TOF 10k could clearly separate the individual peaks in the mass spectrum. Additionally, a fourth isobar was found that was "hidden" in right slope of the carveol peak for the 5,000 m/Δm resolution device.
For nosespace analysis during and after the consumption of food the situation becomes even more complex, as in addition to the food constituents, potentially isobaric room air and endogenous compounds from human metabolism appear in the mass spectrum. In a non-targeted evaluation of PTR-TOF 10k nosespace data during the consumption of chocolate at nominal m/z 123 three isobars could be unambiguously assigned to a contamination in the sampling setup, a room air compound, and a compound originating from chocolate (tentatively identified as trimethylpyrazine), respectively.
In summary, we were able to show that the extreme mass resolution of the PTR-TOF 10k offers indispensable advantages for food research. In this field, more (resolution) is indeed better.
IONICON is the world's leading manufacturer of ultra-sensitive real-time trace gas analyzers based on the unique Proton Transfer Reaction – Mass Spectrometry (PTR-MS) and proprietary SRI-MS technology. IONICON also produces industrial process monitoring solutions, modular time-of-flight (TOF) mass spectrometers for research & OEM, and offers analytical services.