Application Note SI-01741
Analysis of Greenhouse Gases by Gas Chromatography
Coen Duvekot
Varian, Inc.
Introduction
Nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4)
are considered to be very powerful greenhouse gases. These
gases absorb the sun’s rays and thus, influence the global
heat budget. Continuous measurement provides insights into
the sources of the different gases. A Varian 450-GC based
system was custom configured to analyze all three gases
in one run in a matrix of atmospheric air containing water
vapor.
Conditions
Sample:
Concentrations: Front EFC:
Middle EFC:
Rear EFC:
Front TCD:
Middle FID:
Rear ECD:
Instrumentation
Technique: Varian 450-GC Gas Chromatograph
Injection: Headspace sampler into a 1041 injector
Detection: TCD, ECD and FID
Table 1. Valve event table.
Vent 1
V 3
Sample loop
500 µL
1041
Sample line purge
Helium
10 1
9
Vent 2
8
7
Flowcontroller
5
6
EFC 24
front
Helium
Column A :
Hayesep N , 80 /100
0.5m x 1/8" SS
10 1
9
3
V 1
Vent 3
4
8
7
EFC 23
middle
Nitrogen or
Argon /
Methane
Column B :
Porapak QS , 80 /100
2m x 1/8" SS
2
3
V 2
6
5
Column C :
Hayesep N , 80 /100
0.5m x 1/8" SS
TCD
Reference
TCD
DEFC 13
front
Carbon Dioxide
Sample
OUT
Sample loop
500 µL
2
Spiked lab air
CO2
0.4 %
CH4
1775 ppb
N2O
320 ppb
17 psi, 40 mL/min total flow
14 psi, 40 mL/min total flow
29 psi, 50 mL/min total flow
Filament Temperature: 200 °C
Block Temperature: 120 °C
Carrier Gas: Helium
300 °C
300 °C
Cell Potential: 415 mV
Make Up Flow: 2.0 mL/min
4
EFC 24
rear
Nitrogen or
Argon /
Methane
Column D :
Porapak D , 80 /100
2m x 1/8" SS
FID
DEFC 11
middle
ECD
DEFC 13
rear
Methane
Nitrous Oxide
Figure 1. Plumbing scheme for the analysis of greenhouse gases.
Time
GSV-1
GSV-2
BF to Vent
V-4
Initial
Fill
Fill
Forward
OFF
0.01
Fill
Fill
Forward
ON
1.00
Inject
Inject
Forward
ON
1.20
Inject
Inject
Forward
OFF
2.05
Inject
Inject
BF
OFF
2.70
Inject
Inject
BF
OFF
Results and Discussion
When conditions were set, as outlined in Table 1, three
chromatograms were obtained. Figure 2 shows the front
channel chromatogram where CO2 was analyzed.
In essence, two channels were used, one of which was
equipped with two detectors. After injection on the first
channel, CO2 and methane were separated from air. The TCD
detected the CO2 and the FID plumbed in series with the TCD
detected the methane. On the second channel, the nitrous
oxide was separated from water. Water was backflushed to
vent and the nitrous oxide detected on an ECD.
Materials and Reagents
Packed columns:
HayeSep® N 80/100 mesh, 0.5 m x 1/8 in. SST
Porapak® QS 80/100 mesh, 2 m x 1/8 in. SST
HayeSep® D, 80/100 mesh, 2 m x 1/8 in. SST
Application Note SI-01741
CO2
0
1
2
3
min
4
5
6
Figure 2. CO2 analyzed on the front detector (TCD).
1 of 2
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Methane was analyzed on the middle channel via FID
detection (Figure 3).
Table 2. Repeatability data on peak area.
Methane
0
1
2
3
4
5
6
min
Run
CO2
CH4
N20
1
13451
2947
900
2
13472
2986
913
3
13477
2928
935
4
13497
2961
929
5
13450
2933
916
6
13482
2996
922
7
13547
2974
875
8
13508
2972
901
9
13535
2967
904
10
13390
2982
904
Average
Std Deviation
RSD %
13481
45.31
0.34
2965
22.51
0.76
910
17.07
1.88
Figure 3. Methane analyzed on the middle detector (FID).
Figure 5 provides a visual impression of the repeatability data
with 10 % variation limits.
Finally, N2O was analyzed on the ECD detector mounted in
the rear position (Figure 4).
Peak Area
16000
14000
12000
CO2
CH4
N2O
10000
8000
6000
N2O
4000
2000
0
0
0
1
2
3
4
5
6
2
4
6
8
10 Run
Figure 5. Repeatability data with 10 % variation limits.
min
Figure 4. Nitrous oxide analyzed on the rear detector (ECD).
To show system suitability, a sample was tested several times.
Repeatability data generated on peak area are shown in
Table 2.
The headspace sampler permits the analysis of samples of
different origin, such as air, water and soil.
On the ECD detector, N2O is analyzed. This, however, can
easily be expanded with CFCs and SF6.
Repeatability data was very good. RSD on peak area below
2 %, for this type of analysis, is excellent.
Conclusion
The Varian 450-GC based system was custom configured in
order to analyze greenhouse gases, carbon dioxide, methane
and nitrous oxide, in one run. The headspace sampler
permitted the analysis of samples of different origin. Air, soil
and water samples can be handled in this way. Repeatability
data indicated that the system was perfectly suited to
greenhouse gas analysis. This system is highly flexible and the
application range can be expanded quite simply to include
CFCs and SF6.
These data represent typical results.
For further information, contact your local Varian Sales Office.
Varian and the Varian Logo are trademarks or registered trademarks of
Varian, Inc. in the U.S. and other countries. HayeSep and Poropak are
registered trademarks of Hayes Separations, Inc. © 2008 Varian, Inc.
Application Note SI-01741
Varian, Inc.
www.varianinc.com
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