Chromatography Forum

Hi,

Please forgive what may seem a very stupid question...
In the coming week, I will need to change out a column from an Agilent GC-MS for a different type and then after a week or so put the original column back on.

Because the ferrules are obviously pretty much welded to the column (and I would have to make fresh cuts either end), this would mean snipping about 1ft of column at the transfer line end (and a few inches at the inlet end) so that I can reinstall. The loss of column length from the transfer line end is something that I would prefer to avoid.

It strikes me that taking off the requisite few inches at what was the inlet end and then plumbing that into the transfer line end and plumbing what was the transfer line end into the inlet would minimise loss of column length, but I would be left with a ferrule about 1ft from the inlet on the column.

Would this approach be acceptable and are there any consequences for having a 'free' ferrule attached to the column?

Kind Regards

R

I'm retired now, but have had experience with Agilent 5971, 5972, and 5973 GCMS instruments.

I would simply leave the existing ferrules in place on column #1, and then re-install that column once you're ready.

And just use new ferrules for column #2.

Is that what you can do?

I'm retired now, but have had experience with Agilent 5971, 5972, and 5973 GCMS instruments.

I would simply leave the existing ferrules in place on column #1, and then re-install that column once you're ready.

And just use new ferrules for column #2.

Is that what you can do?

Hi CPG,

Thanks for your response...
My issue really lies around the fact that reinstallation of the old column necessitates me taking at least a few mm off the end of the column on both sides so that I have a nice clean cut. Not a big deal with the inlet side as I'm only losing a couple of cm after cutting beyond the ferrule. On the transfer line side it's a different story... if I just pop it back in (having lost a few mm to ensure a clean end), the end of the column will not correct have the correct depth in the source and will in fact terminate outside of the source. The only way to address this is to cut beyond the ferrule (losing 1ft or so of column) or flip the column the other way around as I was pondering in the original e-mail.

Easier to see than to explain!

Kind Regards

R

1. If your column is a modern bonded relatively non-polar column, I would just leave the outlet end uncapped while it sits unused, and not trim that end.

2. How long is your column? Trimming a foot or so at the MS end is not a huge percentage of loss for typical GCMS columns.

3. Could it be time to purchase/use a brand new column?

4. Maybe consider a semi-permanent short transfer line which stays in place and just use a union to connect your columns to that.

Why would you need to re-trim the ends? I would simply remove the column, store it with the nuts and ferrules in place, and then re-install it. If you want to seal the ends then you can get tapered glass caps, or connect the inlet and the outlet with a press-fit connector, but put them on very lightly or they will stick and damage the ends.

Dear Both,

Thanks for your excellent responses. I learned that I don't need to constantly snip the column and that will certainly make for an easier life going forward.

Ironically, I did remove the column this morning and was rewarded with a ferrule which (as it was warm) had unexpectedly expanded enough for the column to be pulled through giving me a lot more flexibility when it comes to reinstallation.

Many thanks

R