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| Titel |
Development of a sensitive long path absorption photometer to quantify peroxides in aerosol particles (Peroxide-LOPAP) |
| VerfasserIn |
P. Mertes, L. Pfaffenberger, J. Dommen, M. Kalberer, U. Baltensperger |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 5, no. 10 ; Nr. 5, no. 10 (2012-10-02), S.2339-2348 |
| Datensatznummer |
250003116
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| Publikation (Nr.) |
 copernicus.org/amt-5-2339-2012.pdf |
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| Zusammenfassung |
A new off-line instrument to quantify peroxides in aerosol particles using
iodometry in long path absorption spectroscopy has been developed and is
called peroxide long path absorption photometer (Peroxide-LOPAP). The new
analytical setup features important technical innovations compared to
hitherto published iodometric peroxide measurements. Firstly, the extraction,
chemical conversion and measurement of the aerosol samples are performed in a
closed oxygen-free (~ 1 ppb) environment. Secondly, a 50-cm optical
detection cell is used for an increased photometric sensitivity. The limit of
detection was 0.1 μM peroxide in solution or
0.25 nmol m−3 with respect to an aerosol sample volume of 1 m3.
The test reaction was done at a constant elevated temperature of
40 °C and the reaction time was 60 min.
Calibration experiments showed that the test reaction with all reactive
peroxides, i.e. hydrogen peroxide (H2O2), peracids and peroxides
with vicinal carbonyl groups (e.g. lauroyl peroxide) goes to completion and
their sensitivity (slope of calibration curve) varies by only ±5%.
However, very inert peroxides have a lower sensitivity. For example,
tert-butyl hydroperoxide shows only 37% sensitivity compared to
H2O2 after 1 h. A kinetic study revealed that even after 5 h only
85% of this inert compound had reacted.
The time trends of the peroxide content in secondary organic aerosol (SOA)
from the ozonolysis and photo-oxidation of α-pinene in smog chamber
experiments were measured. The highest mass fraction of peroxides with
34% (assuming a molecular weight of 300 g mol−1) was found in
freshly generated SOA from α-pinene ozonolysis. Mass fractions
decreased with increasing NO levels in the photo-oxidation experiments. A
decrease of the peroxide content was also observed with aging of the aerosol,
indicating a decomposition of peroxides in the particles. |
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