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Interferences in the determination of formaldehyde via PTR-MS: What do we learn from m/z 31?

: Schripp, T.; Fauck, C.; Salthammer, T.


International journal of mass spectrometry 289 (2010), Nr.2-3, S.170-172
ISSN: 0168-1176
ISSN: 0020-7381
ISSN: 1387-3806
Fraunhofer WKI ()
formaldehyde; breath analysis; PTR-MS; fragmentation

The determination of trace levels of formaldehyde in air via Proton-Transfer-Reaction-Mass-Spectrometry (PTR-MS) has been reported in several publications. Especially in case of breath analysis - an important field for PTR-MS measurements - relatively high formaldehyde concentrations were found. However, due to the low mass of the target compound interferences from fragment ions of larger molecules are likely. In this study breath analysis aiming at the determination of formaldehyde via PTR-MS and online-formaldehyde analysis (basing on the Hantzsch reaction) is performed. The presence of alcohols obviously increased the amount of detected m/z 31 while no change of the online-analyzer signal occurred. Additionally, the determination of the rate constant k(f) of the formaldehyde ionization in the PTR-MS is performed on the basis ofernission chamber tests. The results illustrate the vast complications when quantifying formaldehyde in air via PTR-MS at m/z 31.