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Online Analyser prblems
Posted: Tue Jan 13, 2009 10:04 am
by humanpj
We are busy with an application to measure CO2 in H2. The sample is a bit wet, and what we are seeing is that during calibration we get a nice big peak. On the process sample there is no peak at all. We took a sample to the lab and they confirm that there is CO2. What can it be.? Can CO2 dissolve so much in water that we do not see the peak?
Posted: Tue Jan 13, 2009 11:16 am
by krickos
Hi
Well you did not disclose much details, this is not my speciality but once when analyzing something completly different with headspace-GC-MSD and a PLOT column I noted that the CO2 peak from the laboratory air vanished in the sample injections (DMAA, basic API+residual water) compared to the blanks (DMAA). So yes it seems like depending on circumstances CO2 dissolve in water and the equilibrum is pushed towards the carbonate ion if water is basic.
So maybe checks on pH is needed?!
Posted: Tue Jan 13, 2009 10:05 pm
by GasMan
Are you using a gas sample valve with a sample loop. I have seen a case where due to a wet sample, the inside of the sample loop had rust present, and the CO2 was being absorbed on the rust.
Gasman