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Topic: Column cleaning - not good...  (Read 2488 times)

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Offline Krkann

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Column cleaning - not good...
« on: March 22, 2018, 06:19:02 PM »
I need an advice. I'm a noob in GC and I recently started doing my MSc thesis on analysis of some terpenes in essential oil. A couple of days ago I did a stupid mistake and run analysis of a sample which was way too concentrated, and now unfortunately I have some unwanted peaks of the heavier compounds I can't remove from the column, I guess (?) the compounds are stuck on the column...

I was "rinsing" the column by running a quick heating program up to 280°C with pure solvents (hexanes, MeOH, DCM...) for a last couple of days, but I always get a forest of stretched peaks above 200°C which don't disappear. It doesn't seem to look like a column leak.

How do I clean the column? It's a MXT-5 packed column.

Edit: I also cleaned the liner and changed glass wool, but it didn't help...

Offline hypervalent_iodine

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Re: Column cleaning - not good...
« Reply #1 on: March 22, 2018, 07:09:27 PM »
Could you give a bit more information about how you're running the GC? Specifically, how quick is a quick heating method, what is the max operating temperature of the column, and what temperature do you run the inlet at when you do a normal run?

If you aren't doing it already, I would suggest that when you bake the column, to remove it and reinstall it the other way around. That way you aren't just pushing crap that is hard to remove further into the column. It may be too late for that if you've already baked it several times with it installed as is, which may also render my next bit of advice somewhat pointless: you can cut the column from the front end by about 30 cm. That's often where the heavy stuff gets stuck (hence why you would reinstall it the other way around when baking). You will probably need to clean or replace your liner, and your detector after you finish baking it. If that still doesn't fix it, I'm afraid you might have killed it. You can keep trying to flush it out, but you will eventually worsen the quality of your column.

Offline wildfyr

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Re: Column cleaning - not good...
« Reply #2 on: March 23, 2018, 08:32:05 AM »
A bakeout is definitely the way to go. It should say on the column what the max temp is. Make a method that sets it to 10-20°C below that, and just run the method for a couple hours. If there is still crap, it means they probably polymerized on the column and are slowly degrading and you need a new column.

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