GC tailing solvent peak

[Rganga]

Hi everyone,
I have a problem with my GC. I did some maintenance work (changing septum, liner, cut of the column front, and detector cleaning). When I tried to start working again, after a 280ºC ramp during 3 hours to stabilize my column. I have a serious solvent tailing, I tried to reduce the injection volume, the inlet temperature. No way, This is the kind of chromatogram I have.
Could you help me please with this. Thank you very much.

http://i55.tinypic.com/15e8pj9.jpg

[Rganga]

I forgot to mention that I have FID detector.
Thanks

[larkl]

Any chance the inlet liner contains glass wool that ISN'T silanized? That would do it.

[AICMM]

Rganga,

It looks to me like you never go splitless. This looks like a classic splitless injection that never "opens" the splitter valve. That being said, it could also be a clogged split line.

Best regards.

[Peter Apps]

If you plot any chromatogram with a low enough attenuation all the peaks look like this - so check that you printout is at the same settings as it used to be.

When you re-intalled the column after trimming the end, did you cut at least 20 mm of the end off AFTER you had threaded it through the ferrule ?. If not you may have a tiny fragment of ferrule inside the column. Examine the first meter of column with a bright light and a magnifier.

Peter

[chromatographer1]

If some graphite entered the column it could be anywhere along the length of the column and give you grief (tailing).

ALWAYS trim a column AFTER inserting it through a ferrule, AND keep the end pointing downward when you trim the column.

best wishes,

Rod

[Rganga]

Thanks to everyone for the valuable insights. What do you think I should do now, I should try to let the system running at 300ºC for example overnight? should I let the FID on or off during this cleaning procedure?
Thanks again
Best regards

[chromatographer1]

I would not run the column hot until you find the cause of the tailing.

Cooking the column won't fix the problem and can do damage if particles are present on the column.

Rod

[AICMM]

Rganga,

The next step I would do is to run the sample as a split injection. If the solvent peak is very sharp then you know the split plumbing is intact. If the split plumbing is intact, the next thing to determine is if the split valve is functioning properly. This is best done by ear and by touch.

If both of these work, then start looking column position, trim the front of the column, liner type, . . .

Best regards.

[Jumpshooter]

R,

The broad appearance of your solvent front peak indicates that your solvent requires approximately 2 minutes to completely elute from the column. What solvent are you using?

To fix this:

1) If you change your GC Method to "Split" injection for the Inlet parameter---peradventure--a 100:1 split then your solvent peak ought to become sharper and elute in less than 3 seconds.

2) adjust the conc. of your extracted test samples so that a 100:1 split would provide at least 1 microgram of analyte onto the column after accounting for the 100:1 split.

As AICMM surmised, you're probably injecting in "Split-Less" mode.

I think an "over night bake off" treatment of the column would be huge waste of your Gases (Helium, Air, Hydrogen)--because there's really nothing to ''bake off".

Try the split flow mode and Report back to us.

[Rganga]

Yes the problem was that the system was on splitless mode, I changed to split and I have a very good solvent peak now. But I do have a very bad tailing peaks. I injected the standard and I have a tailing peaks. What could be the reason, the gas flow? should I reduce it? I am working with constant pressure at 14.5,
The solvent I am using is Hexane. And I am analysing fatty acids methyl esthers.
Thanks very much. Your help is really very useful for me. Thanks again.

[chromatographer1]

You should check the proper depth of installation of the column in the inlet and the detector.

Make sure that you have nice clean cuts on both ends.

Your inlet should be clean and not have a lot of flashed back deposits upstream in your pneumatics. You should not be injecting too large an amount of solvent.

Good luck in your troubleshooting.

Rod

[AICMM]

Rganga,

Rod's advice about checking column installation is critical. Have to do that first.

If that is okay, then you need to post a lot more information. Column dimensions, phase type, amount injected (on-column amount), oven operating conditions, liner type, etc, etc...

Best regards.

[Rganga]

Thank you all for your asistance,
I checked the distances of the column at the injector and detector parts (FID). I changed the septum and the liner.
I still have a tailing peaks.
My GC is used for fatty acids methyl esthers analysis.
The column is: supelco 30m * 0.32mm*0.25 mm.
The method is : 170 ºC for 10 min, then a rampe of 2.5 to 220, and then 220ªc for min. The constant pressure is 14.5pa.
the injector temp is 220 and the FID temp is 240ºC.
I did a FID (only stainless parts) cleaning with Decon + sonication for 15min and acetone at 100ºC.
What should I do to improve my peaks?
Thank you very much again,

RG

[Peter Apps]

Have you checked that there is no dirt in the inlet below the liner ?

It looks as if there is a problem with the column. Since this is related to removing and reinstalling it, I still suspect that a fragment of ferrule got inside the column. To eliminate this possibility, put in an new column. If the tailing is better with the new column you mihgt be lucky enough to be able to see a fragment of ferrule inside the column, if you do and it is close to the end of the column you can cut that piece off.

Peter