Simultaneous measurement of greenhouse gases (CH4, CO2 and N2O) using a simplified gas chromatography system

Abstract

This article presents a simple method for determining greenhouse gases (CH4, CO2 and N2O) using an alternative new set-up of the chromatographic system. The novelty of the presented method is the application of a Carboxen 1010 PLOT capillary column for separation of trace gases – CH4, CO2 and N2O – from air samples and their detection using a barrier discharge ionisation detector (BID). Simultaneously, a parallel molecular sieve column RT-Msieve 5A connected to a thermal conductivity detector (TCD) allowed the determination of CH4, N2 and O2 concentrations from 0.2 % to 100 %. The system was equipped with an autosampler transferring the samples without air contamination thanks to a vacuum pump and inert gas flushing. Method validation was performed using commercial gas standards and comparative measurement of CO2, CH4 and N2O concentrations applying cavity ring-down spectroscopy (CRDS). A 3 d continuous measurement series of greenhouse gas (GHG) concentrations in ambient air and tests of typical vial sample measurements with increased GHG concentrations were performed. The advantage of this method is that the system is easy to set up and allows for simultaneous detection and analysis of the main GHGs using one gas chromatography (GC) column and one detector, thereby omitting the need for an electron capture detector (ECD) containing radiogenic components for N2O analysis and a flame ionisation detector (FID) with a methaniser for low-concentration CO2 samples. The simplification of the system reduces analytical costs, facilitates instrument maintenance and improves measurement robustness.