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| Titel |
A dielectric barrier discharge based ion source for a sensitive and
versatile chemical ionization time of flight mass spectrometer instrument
using the negative ion mode |
| VerfasserIn |
Sascha Albrecht, Armin Afchine, Jochen Barthel, Markus Dick, Heinz Rongen, Joachim Franzke, Fred Stroh, Thorsten Benter |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250141546
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| Publikation (Nr.) |
 EGU/EGU2017-5071.pdf |
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| Zusammenfassung |
| Chemical ionization mass spectrometry (CIMS) provides high sensitivity for ultra-sensitive
trace gas measurements in the atmosphere. The presented ion source is used to replace
radioactive Po ion sources. First in-field test runs have been done using an airborne
instrument flown on the StratoClim campaign in Greece, Kalamata 2016. Especially
stratospheric measurements at ambient pressures lower than 100 hPa require improved
sensitivity. Therefore, a chemical ionization (CI) time-of-flight (TOF) instrument using a
dielectric barrier discharge (DBD) ion source and a high-transmission transfer stage has been
set-up and characterized. A new concept including the ion molecule reaction (IMR) zone
inside an ion funnel is used.
The focus will be on the brilliant DBD ion source, which also can be used to generate ion
precursors in the plasma. Thereby multiple reactants can be generated having a versatile ion
source. To finally judge the brilliance of the DBD ion source it is compared to a 10 mCi Po
ion source. These measurements are highlighting that even more ions are generated in the
DBD ion source compared to a 10 mCi Po ion source. However, first measurements with
good sensitivity have been made, employing the CIMS instrument described. The analyte gas
is introduced into the first ion funnel and mixed with the ion source gas flow. It has been
discovered that the mixing in the IMR funnel is critical in terms of sensitivity and was
therefore optimized. The ion funnel achieves a transmission of 40% working at 50 hPa
pressure and using a gas flow of 1 slm. The complete transfer stage achieves a high
transmission of around 10 % for gas phase ions and therefore enables a high sensitivity
combined with the brilliant DBD ion source. A detection limit better than 100 pptV was
determined for SO2 using CO3− ions. Further-on a fast exchange of the reactants
is possible. NO3−, CO3−, I− and SF6− have been successfully tested and can
be generated in the DBD from low ppm or even ppb amounts of their precursor
molecules. This allows a fast exchange of the reactant chemistry within minutes
and gives a wide range of analytes for measurements using chemical ionization. |
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