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Greenhouse Gases analysis by a modified Agilent HS-GC/FID/ECD System
Application Note
Authors:
JL González, M Gibert, JR Gibert
Ingenieria Analitica SL
Abstract
An analytical method based on a modified Agilent 7697A Headspace coupled to a 7890A GC system
was developed for Greenhouse gases (CH4, CO2, N2O) analysis using only one column and two different
detectors (FID and micro-ECD). This configuration permitted the possibility to analysis air sample from
vials and calibration gas from an external 3-ways valve. The method allows separating in one injection CH4,
CO2, N2O in a 20-min cycle with good accuracy and high sensitivity required to measure these gases in
ambient air and soil samples.
Introduction
Greenhouse gases such as carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) have the
capability to change the Earth temperature. Their measurement provides important information about
greenhouse gas emission and permits to control and understanding climate changes.
In this application an Agilent HS 7697A coupled to a GC 7890A with FID-ECD detectors was
configured with a volatile interface, only one switching valve, a methanizer and one column that permits the
CH4, CO2, N2O separation and detection by FID and ECD simultaneously in one analysis at ppbv levels in
ambient air and soil samples.
Experimental
Channel 1 for CH4 and CO2 components was configured as follows:
-
1 mL loop controlled by HS 7697A
-
Volatile Interface VI
-
Specific Capilary column (P/N KRCIAES6017)
-
Methanizer
-
FID detector
Channel 2 for N2O component was configured as follows:
-
1 mL loop controlled by HS 7697A
-
Volatile Interface VI
-
Specific Capilary column (P/N KRCIAES6017)
-
uECD detector
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Results
The following picture shows the characteristic chromatogram of Gas Standard and the two channel
ECD (N2O 0.1ppm) and FID (CH4 0.5ppm, CO2 200ppm) detection systems, respectively.
The following picture shows the characteristic chromatogram of Ambient Air and the two channel
ECD (N2O 0.3ppm) and FID (CH4 2.5ppm, CO2 275ppm) detection systems, respectively.
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As shown in the pictures above, the method permits to separate these components (CH4, CO2 and N2O)
with an appropriate specificity and selectivity from standard and real sample. The method permits also to
analyze these compounds from soils using the Headspace instrument.
The following table shows the performance of the method. The present configuration permits to analyze
CH4, CO2 and N2O in only one injection with a good precision (< 2.1%) and good sensitivity (CH4
160ppbv, CO2 250ppbv, N2O 38ppbv) for a signal-to-noise of 10.
CH4
CO2
N2O
CH4
CO2
N2O
AREA
SD
RSD %
ppbv (SN=10)*
4.8
1810
93
0.1
4
2
1.5
0.2
2.1
160
250
38
Rt min
SD
RSD %
1.78
3.33
4.85
0.002
0.002
0.001
0.1
0.05
0.02
* Limit of Quantitation at signal-to-noise of 10
Conclusions
The present application consists in a very simple configuration using a modified Agilent 7697A
Headspace coupled to a 7890A GC system, one analytical column and two channels for FID and uECD
detection in a total cycle of 20min.
The method permits the separation of CH4, CO2 and N2O with a good specificity and selectivity at
ambient air levels.
The methods allows quantify these three components in ambient air with a good analytical precision (<
2.1%), chromatographic stability (< 0.1%) and a good sensitivity al ppbv levels.
References
Wang Ch. Simultaneous Analysis of Grrenhouse Gases by Gas Chromatography. Application
Environmental 59990-5129EN. 2010.
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