Problem when changing a column

[KevinBe]

Dear all,

Please don't laugh but I have a problem when changing a column in a thermo GC FID...

I'm usually not the one in charge and far from being a specialist.

But here is my problem:

First of all, I'm not exactly sure which mark on the Thermo ruler I should use to set the length that goes into the injector. My liner is a simple straight liner without any thing special. I did chose the length for splitless but maybe I should have used split or split with OC needle? I'm not sure.

Anyway, I installed my column after cutting both ends and did a leak test. it was awfully leaking and I tried to fix it by tightening the bolts with the ferrules. It was still leaking but less.

I turned the gc on and after conditioning I tried to a run with simply acetone and some chiral compounds (the column is chiral) but I did not see any peaks at all... Just a drifting baseline (not much though)

I tried to unscrew the bolts with the ferrule and ... back luck... I did tight them too much and the ferrules are stuck on the screws... (Did I clogged the column by doing that?). I think I will have to pull carefully on the column to avoid breaking it and get the ferrule back and try to remove it from the column.

I'm a bit puzzled by the fact that the column was tightly fixed (too tight actually...) and I still have leaks... I double checked the injector region by screawing everything tightly and changing the septum but without luck.

So after spending hours on this GC I would be happy to get any suggestions on what should have been an easy column change...

Cheers,

KL

[CE Instruments]

Injection depth , probably for split as you have a split liner in it.
Thermo use graphite ferules that will just keep on compressing you should never have to tighten much tighten more than finger tight.

What else did you undo in changing the column ? Most common leaks are the liner seal if you took the liner out and the septa. It won't leak from the detector end so really don't over tighten there !

The ferrules will stick if you over tighten , use a small screw driver or similar to prise the steel cap away from the body connection.

No point running unless it passes the leak test. Did you run the column eval first ? Did it pass ?

Re the trace , is the FID lit ? Description hints it may not be lit. Are you sure the column is the correct distance into the FID, you don't get a trace if it is out through the jet

[Peter Apps]

Hi KL

In addition to what CEI said ...

It is really important that you do not heat the column up again (as in conditioning it) unless and until you have a leak-tight system. Oxygen from the air diffuses in through leaks and will destroy your stationary phase at high temperature.

Peter

[DR]

Also (another general tipfor capillary columns) - first put ferrules on column, then make clean cuts at both ends prior to inserting them to proper depths and snugging ferrule nuts on. This prevents clogged column issues as it is more or less impossible to slip a column through a graphite ferrule without shaving a bit of material and depositing it in the tip of the column.

[KevinBe]

Thank you so much!

I reinstalled the column. Still leaking but not much.

I have a problem with the column evaluation! When i pressurize the colum to 100 in the carrier menu, I see a flow but I don't get any flow in the column eval menu. Any idea why?

Thanks you