TY  - JOUR
AU  - Albrecht, Sascha R.
AU  - Novelli, Anna
AU  - Hofzumahaus, Andreas
AU  - Kang, Sungah
AU  - Baker, Yare
AU  - Mentel, Thomas
AU  - Wahner, Andreas
AU  - Fuchs, Hendrik
TI  - Measurements of hydroperoxy radicals (HO<sub>2</sub>) at atmospheric concentrations using bromide chemical ionization mass spectrometry
JO  - Atmospheric measurement techniques discussions
VL  - amt-2018-195
SN  - 1867-8610
CY  - Katlenburg-Lindau
PB  - Copernicus
M1  - FZJ-2018-06586
SP  - 1 - 19
PY  - 2018
AB  - Hydroxyl and hydroperoxy radicals are key species for the understanding of atmospheric oxidation processes. Their measurement is challenging due to their high reactivity, therefore very sensitive detection methods are needed. Within this study, the measurement of hydroperoxy radicals (HO2) using chemical ionization combined with an high resolution time of flight mass spectrometer (Aerodyne Research Inc.) employing bromide as primary ion is presented. The 1σ limit of detection of 4.5×107moleculescm−3 for a 60s measurement is below typical HO2 concentrations found in the atmosphere. The detection sensitivity of the instrument is affected by the presence of water vapor. Therefore, a water vapor dependent calibration factor that decreases approximately by a factor of 2 if the water vapor mixing ratio increases from 0.1 to 1.0% needs to be applied. An instrumental background most likely generated by the ion source that is equivalent to a HO2 concentration of 1.5±0.2×108moleculescm−3 is subtracted to derive atmospheric HO2 concentrations. This background can be determined by overflowing the inlet with zero air. Several experiments were performed in the atmospheric simulation chamber SAPHIR at the Forschungszentrum Jülich to test the instrument performance by comparison to the well-established laser-induced fluorescence (LIF) technique for measurements of HO2. A high linear correlation coefficient of R2=0.87 is achieved. The slope of the linear regression of 1.07 demonstrates the good absolute agreement of both measurements. Chemical conditions during 15 experiments allowed testing the instrument’s behavior in the presence of atmospheric concentrations of H2O, NOx and O3. No significant interferences from these species were observed. All these facts are demonstrating a reliable measurement of HO2 by the chemical ionization mass spectrometer presented.
LB  - PUB:(DE-HGF)16
DO  - DOI:10.5194/amt-2018-195
UR  - https://juser.fz-juelich.de/record/857601
ER  -