Chromatography Forum

Hello all,

I have been experiencing a very weird problem with the Varian GC/IT-MS Saturn 4000 system. The system is configured in internal ionization mode.
I cleaned the entire system and the column there installed is new (RTX-5 amine). Since the cleaning, I have analyzed alkanes, PAHs, BTEX, fragrance compounds and even Grob Test Mix with no problem. However, every time I try to run triazole compounds (pesticides) the tailing is huge.
I tried so far: liquid injection (splitless and varying split), SPME, changed column, changed trap temperature (where I saw a small improvement, but still too much tailing).
I am at lost here. I don't even know where to start this throubleshooting. Any help, suggestion is more the very well welcome!!!!

You may have figured out the issue already but I figured I would respond anyway.

It sounds like you already gave it a pretty good start for troubleshooting

Since the tailing is compound specific it is probably still have an active site at or near the injection port of the GC system. I assume by "cleaning" you replaced the liner and clipped part of the column etc (if needed). I assume you have different liners for liquid injection and SPME injection. Do either of them have glass wool? If so this can cause tailing of some compounds. For most pesticides analyses it is usually recommended to use deactivated liners such as Siltek coated or Restek's new Sky Blue liners. Both are optimized for the least amount of tailing and chemical breakdown. If you're sure it's not liners the only other thing that I can think of is that the injection port itself is dirty and needs to be removed and cleaned by sonication in solvents. If you have any other information about the cleanings you have done or specifics of the analysis it might help.