Gas chromatography
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I have a question: For the analysis of trace amounts of CO2/CO in gases, which type of detector is more suitable for use with gas chromatography?
The Thermal Conductivity Detector (TCD) is inexpensive but has low sensitivity; it is mainly used for gas detection；
Thank you. But with trace amounts of CO2, won’t the low sensitivity of the thermal conductivity detector prevent it from detecting them?
For trace amounts of carbon monoxide and carbon dioxide in gases, a methanation converter equipped with an FID detector is required when using chromatographic analysis. The methanation converter is used to hydrogenate carbon monoxide and carbon dioxide into methane, which is then detected using a FID detector, thereby greatly improving sensitivity. This configuration is the standard conventional one. This method is used for the detection of trace amounts of carbon monoxide and carbon dioxide in some gas products. Those who say to use a thermal conductivity detector basically have no understanding of the analysis of such samples.
Currently, the FID uses units on the PPM level; indeed, the sensitivity of the CO/CO2 TCD is not sufficient.
So how can one distinguish between carbon monoxide and carbon dioxide?
Based on your reply, it is recommended that you take a look at the basic information on chromatography. Chromatography is first and foremost a separation technique, and only secondly an analytical detection technique. The characteristic of chromatography is separation first, followed by detection, got it? If you don’t understand it, it is recommended to read another introductory book on chromatography.
Recommended configuration: methanizer, air purifier, FID detector.
For things like analyzing the carbon dioxide content in the air, a TCD is sufficient; of course, this assumes that you have valves to isolate the CO2. If the concentrations are trace levels, it’s better to use a methane converter along with an FID for measurement.