I need to detect H2, CO, CO2 and CH4. I have an SRIGC which uses TCD detector, He carrier and has 2 columns Molecular sieve and HayesepD. I used He and N2 carriers but am not satisfied with either(N2 detects H2 but not others, He detects non-H2 but does not give a big enough peak for H2). I was thinking of using Neon as carrier (as the Thermal cond of Ne is much higher than N2 but lower than He).
Has anyone used Ne carrier with TCD and if so how was it's sensitivity and sepapration ability with the above gases?
By Gas_man on Monday, April 12, 2004 - 07:50 am:
Working for one of the major instrument suppliers and being involved with gas analysis and analyzers on a global basis, I have never had a request to use neon as a carrier gas. The analysis that you are trying to do is common, and the problem is hydrogen at below 10% with helium as carrier gas. The results are not predictable, as the response is a curve/straight line. Above 10% you will see a straight line with negative response. As you decrease the concentration, you will go through zero response and you will be on a curve which will return back to zero response for 0% of hydrogen.
For this reason, most people will use nitrogen or argon as a carrier gas for the hydrogen analysis. This will mean two injections and two channels.
I am not familiar with the SRIGC, but if this uses a traditional Wheatstone bridge TCD is may be possible to set up the 'reference' side with nitrogen and use this to measure hydrogen. Many manufacturers use this approach when faced with this analysis.
By Les on Monday, April 12, 2004 - 04:04 pm:
What temperature settings for the TCD? Usually try to keep low as possible. Set the temp around 150C and see if sensitivity increases.