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| Titel |
The effect of relative humidity on the detection of pyrrole by PTR-MS for OH reactivity measurements |
| VerfasserIn |
V. Sinha, T. G. Custer, T. Kluepfel, J. Williams |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250025737
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| Zusammenfassung |
| The hydroxyl radical (OH) is the most important atmospheric oxidant. Recently Sinha et al.
[1] developed a new method to measure the total OH reactivity of ambient air (OH sink)
employing a proton transfer reaction mass spectrometer (PTR-MS) as a detector. The new
method uses pyrrole (C4H4NH) as a reagent and for an OH reactivity measurement this
species must be measured under both dry (~ 0% RH) and humid air ( > 30% RH). Here, we
investigate the sensitivity dependence of the PTR-MS for pyrrole, as a function of relative
humidity in the sampled air. Various normalizations with respect to the H3O+ ion and its
different hydrated clusters ions H3O+(H2O)n=1,2,3 are compared. It is shown that both the
primary ion signal (H3O+ ion m/z = 19) and the first water cluster ion H3O+(H2O) (m/z
= 37) should be used for pyrrole quantification. However, in spite of using this
normalization, the PTR-MS sensitivity for pyrrole changes by as much as 16 % between
dry (~ 0% RH) and humid air (above 30 % RH), with higher sensitivity when the
sampled air is humid. Thus, for accurate quantification of pyrrole using a PTR-MS,
calibration factors appropriate to dry and humid air should be employed. We recommend
that humidity dependence of the PTR-MS be taken into account when reactivity
measurements are performed using the pyrrole based comparative reactivity method
(CRM).
[1]. V. Sinha, J. Williams, J.N. Crowley, and J. Lelieveld, Atmos. Chem. Phys. 8 (2008)
2213-2227 |
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