Chromatography Forum

I installed a guard column with my analytical column for the first time. Guard column on inlet end.

Checked for leaks - none. Helium through column present (placed free end in methanol to check).
Conditioned column for 8 hours

Installed into MS, ran blanks. baseline rise, column bleed present.

Leak? Although, I did not detect it prior to conditioning column.

With that long of column conditioning (8 hours), if there was a leak present, the integrity of the column is questionable? Is there a chance that the contamination was kept to just the head of the column.

Troubleshooting since column bleed: Approximately 2 meters were trimmed from the head of the analytical column.

I typically haven't conditioned my new capillary columns for years now. Reason is that the columns are all pre-run by manufacturer inside a GC (chromatogram is provided with each column, so it has already gone through a GC programming cycle).

Remember - not everything I do is correct.

It is not clear whether the column was new - if it was a used column then the "bleed" could be heavy contaminants slowly eluting.

Peter

Did you check the ferrules , they must be graphite/vespel types for MS , not pure graphite.

Type and age of column of column? What was the condition of the column before installation?
What was the treatment of the guard column?
How did you connect them?
Temperature range ramp and used for conditioning?
What grade of carrier gas are you using, do you have an indicating trap on the instrument?
What was the head pressure of the instrument throught the conditioning run and were you running split or splitless?

A column in unknown condition leaves us no information as to wether a change has taken place.
The other questions relate to some things that can be done to damage a column - particularly taking the column over temperature or inadvertant introduction of air at high temperture over a long period of time.

Did you check the ferrules , they must be graphite/vespel types for MS , not pure graphite.

Not OP, but I did not know this.

Why not straight graphite?

...
Why not straight graphite?

"The 15% graphite/85% Vespel ferrules are
used at the MS interface as they are non-porous to
oxygen, thus prohibiting oxygen from entering the MS."

from: Thermo Technical Note 20580.

The big problem with 100% graphite is that they are very soft and will creep - with loss of the seal between the column and the fitting. You need to tighten ferrules ocasionally - graphite more often and after a while you have extruded all the graphte to wherever it goes. With a a mass spec, you have some risk of graphite fragments being sucked into the instrument and interfering with the electronics.

I installed a guard column with my analytical column for the first time. Guard column on inlet end.

Checked for leaks - none. Helium through column present (placed free end in methanol to check).
Conditioned column for 8 hours

Installed into MS, ran blanks. baseline rise, column bleed present.

Leak? Although, I did not detect it prior to conditioning column.

With that long of column conditioning (8 hours), if there was a leak present, the integrity of the column is questionable? Is there a chance that the contamination was kept to just the head of the column.

Troubleshooting since column bleed: Approximately 2 meters were trimmed from the head of the analytical column.

Agilent recomends against conditioning a colunmn from more than two hours.