O2, CO2 and CH4 with ShinCarbon ST 80/100 2mx2mm (TCD + FID)

[Noxi]

Hello everyone,

I am a PHD student, and I try to learn to use a GC-17A to analyze these different compounds: O2, CO2, CH4, H2S.
I reach out CH4 (retention time 6.4 min) without any problem on a FID with a ShinCarbon ST 80/100 Packed 2m x 2mm, and H2S on a PFPD with a GasPro 0.32x 30m. I have a methanizer, which will allow me to have the CO2 on the FID.

I have a TCD that I could put in series with the FID. But I wonder if the ShinCarbon will be able to correctly separate O2?
I did a search in the forum, but the posts are quite old, and I'm not sure I have the correct answer, nor the right configuration.

Here is a diagram of my current setup:
The flow rate in line 1 is 20 mL/min, oven temperature is 65°C.


If necessary, I have in reserve a-6-port valve, a column Porapak Q 80/100, and a column Moil Sieve 5A.

Thank you in advance for any answer !

[GasMan]

Check out this site. It will give you an idea on what can be separated on different lengths of Shincarbon column.
We have found that 50/80 mesh works similar to 80/100 mesh

http://www.hichrom.com/assets/Products/ ... N-ST_E.PDF

Gasman

[Noxi]

Perfect this document, it is very useful, thank you ! Unfortunately for me, I believe my column will not be long enough to separate nitrogen from oxygen: /

[GOM]

Hi

With regards to separating oxygen and nitrogen, you say that you have a Mol sieve 5A column. This will do that for you. It just needs to be conditioned properly at a high temperature

Regards

Ralph

[GasMan]

GOM is correct in that a Mol Sieve 5A will separate O2 and N2. However, these columns do not like CO2 and H2S. As I see it, you have a choice to make. You either need to order a longer ShinCarbon column or you will need to add another valve to your GC and also add a Porapak type column. The extra valve would need to be a column isolation valve, the column being isolated would be your 5A column. You would then inject your sample into the Porapak column, which would allow O2,N2 and CH4 to pass through quickly into the 5A column where they would be isolated while the CO2 and H2S elute to your TCD bypassing the 5A column. Once they have eluted, you switch the 5A column back into the carrier stream so that O2, N2 and CH4 can elute.

Gasman

[GOM]

oops - sorry I hadn't realised that problem with H2S.

In addition to Gasman's previous Shincarbon reference article I came across this article, which is also quite a good summary comparison of 5A and Shincarbon

http://blog.restek.com/?p=10643

Regards

Ralph