Technical Note: Intercomparison of formaldehyde measurements at the atmosphere simulation chamber SAPHIRReport as inadecuate

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1 Institut für Ionenphysik und Angewandte Physik 2 Atmospheric Chemistry Division Boulder 3 Institut für Chemie und Dynamik der Geosphäre 4 Institut für Meteorologie u. Klimaforschung 5 Leibniz-Institut für Troposphärenforschung ift 6 Institut für Umweltphysik

Abstract : The atmosphere simulation chamber SAPHIR at the Research Centre Jülich was used to test the suitability of state-of-the-art analytical instruments for the measurement of gas-phase formaldehyde HCHO in air. Five analyzers based on four different sensing principles were deployed: a differential optical absorption spectrometer DOAS, cartridges for 2,4-dinitro\-phenyl\-hydrazine DNPH derivatization followed by off-line high pressure liquid chromatography HPLC analysis, two different types of commercially available wet chemical sensors based on Hantzsch fluorimetry, and a proton-transfer-reaction mass spectrometer PTR-MS. A new optimized mode of operation was used for the PTR-MS instrument which significantly enhanced its performance for online HCHO detection at low absolute humidities. The instruments were challenged with typical ambient levels of HCHO ranging from zero to several ppb. Synthetic air of high purity and particulate-filtered ambient air were used as sample matrices in the atmosphere simulation chamber onto which HCHO was spiked under varying levels of humidity and ozone. Measurements were compared to mixing ratios calculated from the chamber volume and the known amount of HCHO injected into the chamber; measurements were also compared between the different instruments. The formal and blind intercomparison exercise was conducted under the control of an independent referee. A number of analytical problems associated with the experimental set-up and with individual instruments were identified, the overall agreement between the methods was fair.

Author: A. Wisthaler - E. C. Apel - J. Bossmeyer - A. Hansel - W. Junkermann - R. Koppmann - R. Meier - K. Müller - S. J. Solomon - R. S



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