Natural gas analysis

Chromatography Forum: GC Archives: Natural gas analysis
Top of pagePrevious messageNext messageBottom of pageLink to this message  By C Cornejo on Wednesday, December 29, 1999 - 08:40 am:

I would like to know if someone can tell me what is a small peak with a shoulder that appears just before the butane in a multidimentional analysis. I could identify all the compounds but this particular one seems to be a ghost peak ( I don't know if it is the wright expression in english) If someone has observed the same thing and can explain me what it is I would be very grateful.
Thanks.


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Bill Jenko on Thursday, January 6, 2000 - 09:28 pm:

Can you give us some more detail here: columns used, make and model of the analyzer? Since multidimensional column systems come in a wide variety of configurations, it will be difficult to guess what causes this shouldering peak without more information.

To me a "ghost" peak is a peak that is not caused by a component of the sample, but rather, some artifact caused by the GC system itself. Try injecting your carrier gas, as though it was a sample. That is, fill the sample loop with carrier gas and inject. Any bumps, dips, ghost peaks or other baseline features you see are artifacts of the GC system itself.


Top of pagePrevious messageNext messageBottom of pageLink to this message  By VCornejo on Friday, January 14, 2000 - 07:54 am:

Bill, sorry for the delay on the answering.
We have a HP 6890 and three packed columns: DC200,molecular mesh,Porapack Q and a capilar one (PONA) I made a mistake in my question requiring. The peak appears before the C3. We inyected propane 97%molar and there's no more peak before it. We supposed that the problem is the valve changing to the PONA when there's a high C1 concentration. Perhaps there are some effect of diffusion. We intented by changing diferent variables, but it didn't dissappear.
If you could tell me some more information about the problem, I would be very grateful.
Thanks.


Top of pagePrevious messageNext messageBottom of pageLink to this message  By ihasegan on Thursday, January 20, 2000 - 03:49 am:

Hello Conejo,
Look at pressure of carrier gas to be at the prescribed value, because if the pressure is different the flow of carrier gas is different and the retention time of the compounds is modified. In this case Run Time Program which change the positions of the valves should be modified for the new retention time. If the pressure is modified just put it at the right value and everythings will be OK.
Bye


Top of pagePrevious messageNext messageBottom of pageLink to this message  By V Cornejo on Monday, January 24, 2000 - 05:53 am:

I could finally solve the problem.
Thank you very much to all of you!!!!


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