Using in situ GC-MS for analysis of C<sub>2</sub>–C<sub>7</sub> volatile organic acids in ambient air of a boreal forest site
An in situ method for studying gas-phase C<sub>2</sub>–C<sub>7</sub> monocarboxylic volatile organic acids (VOAs) in ambient air was developed and evaluated. Samples were collected directly into the cold trap of the thermal desorption unit (TD) and analysed in situ...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-01-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | http://www.atmos-meas-tech.net/10/281/2017/amt-10-281-2017.pdf |
| Summary: | An in situ method for studying gas-phase C<sub>2</sub>–C<sub>7</sub> monocarboxylic
volatile organic acids (VOAs) in ambient air was developed and evaluated.
Samples were collected directly into the cold trap of the thermal desorption
unit (TD) and analysed in situ using a gas chromatograph (GC) coupled to a
mass spectrometer (MS). A polyethylene glycol column was used for separating
the acids. The method was validated in the laboratory and tested on the
ambient air of a boreal forest in June 2015. Recoveries of VOAs from
fluorinated ethylene propylene (FEP) and heated stainless steel inlets ranged
from 83 to 123 %. Different VOAs were fully desorbed from the cold trap
and well separated in the chromatograms. Detection limits varied between 1
and 130 pptv and total uncertainty of the method at mean ambient mixing
ratios was between 16 and 76 %. All straight chain VOAs except heptanoic
acid in the ambient air measurements were found with mixing ratios above the
detection limits. The highest mixing ratios were found for acetic acid and
the highest relative variations for hexanoic acid. In addition, mixing ratios
of acetic and propanoic acids measured by the novel GC-MS method were
compared with proton-mass-transfer time-of-flight mass spectrometer
(PTR-TOFMS) data. Both instruments showed similar variations, but differences
in the mixing ratio levels were significant. |
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| ISSN: | 1867-1381 1867-8548 |