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| Titel |
New SI-traceable reference gas mixtures for sulfur hexafluoride (SF6) at the pmol/mol level using static and dynamic preparation methods and comparison to existing scales |
| VerfasserIn |
Simon A. Wyss, Myriam Guillevic, Martin Vicar, Gerard Nieuwenkamp, Martin K. Vollmer, Céline Pascale, Stefan Reimann, Bernhard Niederhauser, Lukas Emmenegger |
| 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 |
250145075
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| Publikation (Nr.) |
 EGU/EGU2017-8971.pdf |
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| Zusammenfassung |
| We developed two SI-traceable methods, using both static and dynamic preparation steps, to
produce reference gas mixtures for sulfur hexafluoride (SF6) in gas cylinders at pmol/mol
level. This research activity is conducted under the framework of the European EMRP
HIGHGAS project, in support of the high quality measurements of this important greenhouse
gas in the earth’s atmosphere.
In the method used by the Czech Metrology Institute (CMI) a parent mixture of SF6 in
synthetic air was produced in an aluminium cylinder at VSL as a first step. This mixture was
produced gravimetrically according to ISO 6142 at an amount fraction of 1 μmol/mol. In the
second step this primary standard was further diluted to near-ambient amount fraction, with
the use of a three-step dilution system and directly pressurised into aluminium cylinders to a
pressure of 10 bars.
The second method used by the Federal Institute of Metrology (METAS) has already been
applied to other fluorinated gases such as HFC-125 and HFC-1234yf. In this method a highly
concentrated mixture is produced by spiking a purified synthetic air (matrix gas) with SF6
from a permeation device. The mass loss of SF6 in the permeation device is observed by a
magnetic suspension balance. In a second step this mixture is diluted with matrix gas to the
desired concentrations. All flows are controlled with mass flow controllers. The
diluted gas was transferred into Silconert2000-coated stainless steel cylinders by
cryo-filling.
The final gas mixtures at near-ambient amount fraction were measured on a Medusa gas
chromatography-mass spectrometry system (Medusa-GC/MS) against working standards
calibrated on existing scales of the Scripps Institution of Oceanography (SIO) and compared
to other scales [1].
The agreement of the assigned values by the CMI and METAS, with the measured values
referenced on the SIO scale was excellent. This results show that with this methods we are
able to produce accurate SI-traceable gas mixtures at near-ambient amount fraction for SF6,
without extensive static dilutions.
[1] Benjamin R. Miller, Ray F. Weiss, Peter K. Salameh, Toste Tanhua, Brian R. Greally,
Jens Mühle, Peter G. Simmonds, Anal. Chem., 2008, 80, 1536. |
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