Recommended # of injections per vial cap/septum?

Hi Brian,

What kind of detector are you using? From my experience with FID, you shouldn’t have issues with septa bleed from re-running samples within the same day. If you inject the vial and then re-run it after a day, you will probably see n-hydrocarbon peaks related to septum bleed. Now this is with a FID, it may be more severe with GC-MS. Also, if you are using septa in your inlet, you’ll want to change that out about every 100 injections.

To add to what Rwilson contributed, don't forget about the sample wash and solvent wash vials.  Those septas will also need replacing or can contribute to septum bleed contamination.

Below are links to two great resources for general good practice.

Better Connections, Better Results with Your Agilent GC System

Don't Fear the Ghost or Unexpected Peaks: Troubleshooting and Prevention

Thanks for the link! I ordered replacement wash vial septa. I'm taking over management of the instrument from previous employees but I suspect they did not maintain that well. 

Thanks for the link! I ordered replacement wash vial septa. I'm taking over management of the instrument from previous employees but I suspect they did not maintain that well. 

Happy to help.

With any future ghost peak troubleshooting you do, keep this in mind about septa contamination, if it is a peak it is likely being introduced at injection and going through chromatography on the column.  If it is a constant background contamination of certain masses, such as showing up even in a tune, it is septa material in the system.

By removing the syringe and performing an injection, you will have a quick test to see if the contamination is in the system or coming from something the syringe is either passing through or pulling solution from.

Don't over tighten the septa cap.  Replace septa on the inlet, wash vials, and change the liner on a regular basis and you will likely eliminate most of your septa contamination problems.

Got it. I did a no-syringe injection to determine the impurities were coming from sample intro. I further confirmed by preparing fresh solvent blank vials with similar results. So that goes back to my original concern: with GC/MS is there a recommended # of injections from the same vial? I suspect part of the issue is using bilayer PTFE/silicone septa with ACN as my solvent. But even if I used rubber/butyl or trilayer septa, is there still a limit on the number of injections from the same vial. 

I should add I am used to LC, so it was very common to use the same vial/cap many many times with no detectable issues by UV or MS.