Chromatography Forum

Hi. I have had an ongoing issue with new trap installs. Does anyone else see this and how do you remedy it?

I am using an Atomx with K trap. The two compounds that split are Dichlorodifluoromethane and Vinyl Chloride. As I run conditioning CCVs, the shape of the split changes from smooth humps to jagged splits. It is not a consistent shape. Overtime, the issue goes away but it takes 24 hours of conditioning sometimes. When I put the old trap in, the issue goes away. I'm thinking it's either the ferrule taking time to expand/contract or the trap adsorbent needing to condition. Anyone?

I had that problem with the K trap in my OI Eclipse, After some nasty samples I changed out the trap. The earliest compounds tailed and or split. No amount of conditioning could fix it. I gave up and put in a new trap, problem went away.

I'm not familiar with the layout of the Atomix, but if the trap can be put in backwards, it will cause all kinds of problems. I had that problem once when I installed a Tekmar 2000 trap in a 3100, the swaged ferrule was on the opposite end of the trap so the strongest adsorbent was first in line instead of last, caused all kinds of problems until I figured out the reversed mounting position.

If you are not using desorb preheat; add this to your program for 1 minute. It should solve your problem.

So, I checked the install and I have the permanent ferrule on the correct side. I also have desorb preheat activated @245C on all of my instruments. I tried reseating the trap with a new ferrule, no change. I wonder if the trap is just no good. Or could it be backwards with the fixed ferrule? The strange thing is that the splitting compounds are first and third on my list. The split does not occur with the 2nd compound which is Chloromethane.That makes me think it is the adsorbent. I guess I need to switch out the trap...

Thank you for your input.

If you have some clean glass wool handy I would first try replacing the glass wool plug at the front end of the trap. Sometimes contaminates can gather there and cause peak shape problems especially if you had a sample that foamed. If that doesn't help then it could be time for a new trap.