Valves and gas sampling loop 7890A

[JulieB]

Hi, I'm new on this forum and I would like to know if there are lovely experts here who could help me with my problem

We want to be able to analyse biogas and natural gas with our GC-TCD-FID-FID. We have a methanizer. There are four packed columns and valves on the GC. We wanted to use Tedlar bags to do the sampling, but now our needs changed and the gas samples would be provided in 500ml gas cylinders instead of Tedlar bags. So, we bought a customized vacuum sampling system, that has 3 valves. I have the diagrams for both the GC and the vacuum sampling system.

I'm not able to do the valve timing properly on the GC. My chromatograms look terrible!

Is there someone with valve knowledge who could help me find a solution, please? I have to say that I'm not a GC expert at all. Any help would be much appreciated. Thank you!!!

[GasMan]

if you can give me the serial number of the GC we can at least see what was delivered. What compounds are you looking for in natural gas?

Gasman

[JulieB]

The serial number of our GC is US11361036.
We are looking for :
C6+, i-C5, n-C5, i-C4, n-C4, C2, C3, CH4 (and CO2, O2, N2).

Thank you in advance Gasman for you help. I will come back on the forum only tomorrow morning (it's the end of my working day here).

[GasMan]

JulieB,

What columns do you already have installed in the GC? The good news is that the valve configurations on your GC are perfect for the natural gas analysis that you wish to do. It is just a question of having the correct columns. Let me know what columns you have.

Gasman

[JulieB]

Hi Gasman,
I believe that I have the right columns, because it's the ones that have been sold to us with our customized GC from Agilent.
Those are the columns that I have :
• Column 1: G3591-80000 UC W982/PAW
• Column 2 : G3591-80001 DC-200/PAW
• Column 3 : G3591-80002 HayeSep Q
• Colonne 4 : G3591-82003 MolSieve 13x

My problem is that the new vacuum sampling system that we just bought, to have more accurate results, is changing all of my valves timing. It's adding three valves to our GC system. How can I mannage to define all of my new retention times and the detectors switching from one to another properly???

I have all the diagrams that I could send you... if you'd like to take a look...
I'm not sure that someone can help me here, but it's not really easy for me to understand my GC system properly. Thank you!!!

[GasMan]

If you have gas samples in cylinders, I do not see any reason to use a vacuum sampling system. I can understand it if you need to draw your sample from a Tedlar bag. Would you please send me the diagram of the sampling system, I already have a valve diagram for your GC. You can send it to DaveTea41@Gmail.com

Did you have the system running at any time giving good chromatograms.

Are you still planning to use the methanizer on this GC and the 4 port valve associated with it? The reason that I ask, is that the 4 port valve can be configured to control your sample and give reproducible results.

Gasman