Chromatography Forum

Hi,

I'm a new user of 7820a for TOGA and we currently installed a Porapak Q metal packed 6ft x 1/8in 80/100 mesh column for FID in tandem with HP-PLOT Molesieve in TCD. I need help in the order of elution of the component gases in FID. The packaging doesn't come with a sample chromatogram. I have a guide in hand but the config is for the JW HP-PLOT Q. I'm not sure if they have the same order, I have doubts.

method config
oven: 40 (for 6min); 24 deg/min (max of 230) till 13.9min
fid heater: 250
h2: 50ml/min
air: 400ml/min

Thanks.


Ivy

I run dissolved gas analysis in transformer oils by ASTM D3612 Headspace. The HP-PLOT Molesieve in TCD will elute as follows:



With column switching with a Carboxen 1006 PLOT (as per ASTM D3612), you should get something looking like this:



time markers are valve actuations between the columns.

Temperature program of ATSM 3612 is like this:



Hope that helps.

Thanks for the info! I have FID for the front, and I'm using Method A (Vacuum Degassing). I have a different one. Seems like my C2's were not separated in a manner like yours. I only have 2 almost overlapping peaks which seems to be the C2 compounds since Q column elute with MW basis. How would I separate these? I wonder if the the baseline really goes up during half time of the bake out process because mine starts to increase at around 11min. I'm in dire need of additional info. Thanks.

Thanks for the info! I have FID for the front, and I'm using Method A (Vacuum Degassing). I have a different one. Seems like my C2's were not separated in a manner like yours. I only have 2 almost overlapping peaks which seems to be the C2 compounds since Q column elute with MW basis. How would I separate these? I wonder if the the baseline really goes up during half time of the bake out process because mine starts to increase at around 11min. I'm in dire need of additional info. Thanks.

I have no experience with Method A (Vacuum Degassing), but the C2's seem to be the easy separation on my system. Perhaps they are methane/CO? They are the hard ones.

In my experience, the PLOT columns are very sensitive to conditioning. They not only bleed a lot but also change their retention and separate better when properly conditioned. Here's the bad baseline drift when I look at a very low concentration sample:

Here's an image of my sample chromatogram:




Valve timing are at 1min, 3, 7 and 13. As I checked, TCD is just HP-Molesieve, not PLOT.

Porapak Q will not seperate ethylene and acetylene.

Gasman

Oh no Gasman, seriously??? Not a chance? Not at all? I mean no matter how you change the config? I remember I saw a sample chromatogram from Agilent's website using Porapak Q with FID and the peaks looked exactly the same. Thought it would separate somehow after slight revisions to thr method config. So therefore if I want the concentration of all my C2 gases, I would have to get another column. Do I have other options? C2 gases are important for TOGA since I'm doing a diagnostic DGA for high voltage equipments.

For the TOGA method A, Agilent uses a Porpak N column. Please see the following relative retention times for the Porapak type packing materials. HayeSep is considered a better version of Porapak. http://www.vici.com/hayesep/rettimes.php

Gasman

Thanks a lot for the info!

Agilent told me to use a different set of columns for Method A as the one I have installed are for Method C. GC 7820A uses a packed column for method config of Method A. So there, my doubts were confirmed. Porapak columns won't work for my method since I need my C2's and C3's separated and quantified.

If you look at the table in the link that I sent to you, you will see that Porapak N will separate the C2's but not the C3's. Porapak R will separate the C3's but not all of the C2's. Agilent has a packed column consisting of a packing of 1:1 HayeSep N and HayeSep R. It is a 8 Foot 1/8 packed column, and can be ordered with the part number G3591-80091 (stainless steel tubing) or G3591-81091 if you wish to use an inert treated stainless steel tubing.

Gasman

Will check on that GasMan. Totally chaotic. I don't have answer from Agilent (nor the local supplier of Agilent) about the method config yet. GC's been stuck for almost a month now. no gc work for me now, but more work is waiting. haha