Issue 9, 2023

Assessment of aldehyde contributions to PTR-MS m/z 69.07 in indoor air measurements


Proton transfer reaction-mass spectrometry (PTR-MS) has been widely used for monitoring outdoor and indoor volatile organic compounds. For outdoor air, mass-to-charge-ratio m/z 69.07 is usually assigned to isoprene. Isoprene is also a major component of human breath and therefore abundant in occupied indoor environments. Mass 69.07 as an indicator of indoor isoprene can suffer interference resulting from fragmentation of aldehydes [V. Ruzsanyi, et al., Multi-capillary-column proton-transfer-reaction time-of-flight mass spectrometry, J. Chromatogr. A, 2013, 1316, 112–118], which are also abundant indoors, especially when ozone is elevated [C. J. Weschler, Roles of the human occupant in indoor chemistry, Indoor Air, 2016, 26, 6–24]. As part of the Indoor Chemical Human Emission and Reactivity (ICHEAR) campaign we examined this effect in human-occupied chamber studies, in the absence and presence of ozone. We find that such interferences do occur when ozone reacts with both human skin oil and cotton-based clothing. In the presence of humans and 35 ppb ozone, PTR-mass 69.07 was three times higher than the isoprene mixing ratio measured independently by GC-MS. To investigate this effect, we measured the fragmentation patterns of aldehydes and examined the contribution of different aldehydes to m/z 69.07 in the ICHEAR experiments. Nonanal, and its contribution to m/z 69.07, could be quantified reliably for clothing and human dermal emissions under the experimental conditions. In contrast, decanal is difficult to quantify, since compounds other than decanal fragment to m/z 157.16, its MH+ peak, which also makes it difficult to estimate decanal's contribution to m/z 69.07.

Graphical abstract: Assessment of aldehyde contributions to PTR-MS m/z 69.07 in indoor air measurements

Article information

Article type
12 Apr 2023
13 Jul 2023
First published
25 Jul 2023
This article is Open Access
Creative Commons BY license

Environ. Sci.: Atmos., 2023,3, 1286-1295

Assessment of aldehyde contributions to PTR-MS m/z 69.07 in indoor air measurements

L. Ernle, N. Wang, G. Bekö, G. Morrison, P. Wargocki, C. J. Weschler and J. Williams, Environ. Sci.: Atmos., 2023, 3, 1286 DOI: 10.1039/D3EA00055A

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

Read more about how to correctly acknowledge RSC content.

Social activity