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VOC run with 64m/z contamination
Posted: Thu Jul 07, 2011 10:04 pm
by 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!
Re: VOC run with 64m/z contamination
Posted: Fri Jul 08, 2011 2:56 am
by 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
Re: VOC run with 64m/z contamination
Posted: Fri Jul 08, 2011 3:34 am
by 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.
Re: VOC run with 64m/z contamination
Posted: Fri Jul 08, 2011 3:02 pm
by Bigbear
Search this forum and the gc forum. There are a number ot threads dealing with 524. If you still have issues ask again.
Re: VOC run with 64m/z contamination
Posted: Wed Jul 13, 2011 8:51 pm
by EnvironLab
Yes, that sounds like a trap issue. I see it now and then.