GC-FID very strange chromatogram

[annie baker]

Hi all

My GC-FID has started producing really weird spectrums. i've just been running hexane cleans through it but the solvent peak is really low (when normally you can't see the top) and it's also a strange rounded peak and very wide. there are also some other peaks that it shouldn't be producing as it's a clean run.

I've just taken apart the split/splitless inlet of the GC-FID i work on and replaced the liner, o-ring, septum, inlet base seal, washer and ferrule and took a bit of the column.
Everything seemed fine apart from that there were loads of odd peaks and the base line was aweful. i then found that the septum had kind of torn itself to pieces so i then has to replace that again and try and clean all the bits out of the whole inlet. I also figured that as i was taking that to bits I may as well clean the detector and collector as well (i did remember to turn the electromitor off). and then when I was putting the column back into the inlet the reducing nut refused to go back in so I changed that too.
this is when it started doing the thing described above.
I have taken it all apart and checked there are no blocks/leaks and all is tight enough, no scratches or nicks on anything but it's still doing it.
I haven't changed the column yet but i've seen damaged columns and it hasn't looked like this before.

As I've taken the whole thing to pieces I now have no idea what could be causing the problem
Has anyone got any clues?

Thanks
Annie

[Peter Apps]

Hi Annie

Welcome to the forum.

What you are seeing is probably the contaminants cooking off the new parts and cleaned surfaces of the inlet. If you are sure that you have no leaks then leave the inlet at its working temperature with a split ratio of 100:1 and the column close to its isothermal maximum overnight and see what it looks like in the morning.

A shredded septum is a sign of a jagged point on the syringe needle. Either replace the needle, or try to file off the jagged end with fine abrasive.

Peter