VOC run with 64m/z contamination

[eauchem]

I am running 524.2 (Aquatek 70/Stratum PTC/Agilent 6890/Agilent 5973N).
Just recently I started getting a large "hump" at the beginning of my run between 2 and 6 minutes (solvent delay until 2 minutes). The predominant mass is 63.8/64 - occasionally there is 79 also. I do not know what this is or where this contamination came from. It is very hard to run low level standards/samples with this interference.
I would appreciate help on this topic.
Thanks!

[nvalentine]

This sounds like water interference to me, which can be an obstacle in 524.2 due to the 25mL sample and 4 minute desorb time for the Purge and Trap. What level standards are you having problems with? If this is a new problem, did you do any maintenance or change anything before this occurred? I know sometimes after cleaning the source it can take some time to get the baseline back down due to residual water. I can probably take a look at a chromatogram and your P&T and GC parameters and see what's going on. My email is nvalentine@teledyne.com if you want some more information or have any specific questions. Hopefully, we can get you squared away.

Nathan Valentine
Applications Lab Manager
Teledyne Tekmar

[nvalentine]

This could also be sulfur dioxide (mass 64) depending on what trap you are using. Again, I'd have to see some data to diagnose.

[Bigbear]

Search this forum and the gc forum. There are a number ot threads dealing with 524. If you still have issues ask again.

[EnvironLab]

Yes, that sounds like a trap issue. I see it now and then.