A versatile, refrigerant- and cryogen-free cryofocusing–thermodesorption unit for preconcentration of traces gases in air
We present a compact and versatile cryofocusing–thermodesorption unit, which we developed for quantitative analysis of halogenated trace gases in ambient air. Possible applications include aircraft-based in situ measurements, in situ monitoring and laboratory operation for the analysis of flask...
Main Authors: | , , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2016-10-01
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Series: | Atmospheric Measurement Techniques |
Online Access: | https://www.atmos-meas-tech.net/9/5265/2016/amt-9-5265-2016.pdf |
Summary: | We present a compact and versatile
cryofocusing–thermodesorption unit, which we developed for quantitative analysis of
halogenated trace gases in ambient air. Possible applications include
aircraft-based in situ measurements, in situ monitoring and laboratory
operation for the analysis of flask samples. Analytes are trapped on
adsorptive material cooled by a Stirling cooler to low temperatures (e.g.
−80 °C) and subsequently desorbed by rapid heating of the
adsorptive material (e.g. +200 °C). The set-up involves neither
the exchange of adsorption tubes nor any further condensation or refocusing
steps. No moving parts are used that would require vacuum insulation. This
allows for a simple and robust design. Reliable operation is ensured by the
Stirling cooler, which neither contains a liquid refrigerant nor requires
refilling a cryogen. At the same time, it allows for significantly lower
adsorption temperatures compared to commonly used Peltier elements. We use
gas chromatography – mass spectrometry (GC–MS) for separation and detection
of the preconcentrated analytes after splitless injection. A substance
boiling point range of approximately −80 to +150 °C and a
substance mixing ratio range of less than 1 ppt (pmol mol<sup>−1</sup>) to more
than 500 ppt in preconcentrated sample volumes of 0.1 to 10 L of ambient
air is covered, depending on the application and its analytical demands. We
present the instrumental design of the preconcentration unit and demonstrate
capabilities and performance through the examination of analyte breakthrough
during adsorption, repeatability of desorption and analyte residues in blank
tests. Examples of application are taken from the analysis of flask samples
collected at Mace Head Atmospheric Research Station in Ireland using our
laboratory GC–MS instruments and by
data obtained during a research flight with our in situ aircraft instrument
GhOST-MS (Gas chromatograph for the Observation of Tracers – coupled with a Mass
Spectrometer). |
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ISSN: | 1867-1381 1867-8548 |