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| Titel |
A field-deployable, chemical ionization time-of-flight mass spectrometer |
| VerfasserIn |
T. H. Bertram, J. R. Kimmel, T. A. Crisp, O. S. Ryder, R. L. N. Yatavelli, J. A. Thornton, M. J. Cubison, M. Gonin, D. R. Worsnop |
| 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 ; 4, no. 7 ; Nr. 4, no. 7 (2011-07-20), S.1471-1479 |
| Datensatznummer |
250002057
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| Publikation (Nr.) |
 copernicus.org/amt-4-1471-2011.pdf |
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| Zusammenfassung |
| We constructed a new chemical ionization time-of-flight mass spectrometer
(CI-TOFMS) that measures atmospheric trace gases in real time with high
sensitivity. We apply the technique to the measurement of formic acid via
negative-ion proton transfer, using acetate as the reagent ion. A novel high
pressure interface, incorporating two RF-only quadrupoles is used to
efficiently focus ions through four stages of differential pumping before
analysis with a compact TOFMS. The high ion-duty cycle (>20 %) of the
TOFMS combined with the efficient production and transmission of ions in the
high pressure interface results in a highly sensitive (>300 ions s−1 pptv−1
formic acid) instrument capable of measuring and saving complete
mass spectra at rates faster than 10 Hz. We demonstrate the efficient
transfer and detection of both bare ions and ion-molecule clusters, and
characterize the instrument during field measurements aboard the R/V Atlantis as part of the CalNex campaign during the spring of 2010. The
in-field short-term precision is better than 5 % at 1 pptv (pL/L), for
1-s averages. The detection limit (3 σ, 1-s averages) of
the current version of the CI-TOFMS, as applied to the in situ detection of formic
acid, is limited by the magnitude and variability in the background
determination and was determined to be 4 pptv. Application of the CI-TOFMS
to the detection of other inorganic and organic acids, as well as the use of
different reagent ion molecules (e.g. I−, CF3O−,
CO3−) is promising, as we have demonstrated efficient transmission
and detection of both bare ions and their associated ion-molecule clusters. |
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