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GC-MS background keeps going up?
Posted: Tue May 28, 2013 11:58 am
by pomerann
Hello,
I've been trying to replicate a run from the previous student in the lab with just plain solvent. The problem is, the background signal of the GC goes up with time. Her runs had backgrounds which were much steadier, and ended at roughly the same height that they began with.
Any clues as to why this happens?
Thank you!
Re: GC-MS background keeps going up?
Posted: Tue May 28, 2013 2:49 pm
by Steve Reimer
Background signal tends to go up with the oven temperature, so check to see that you are running the same program. Also, if you are running solvent blanks check the scale on the Y axis. The difference may be due to display autoscale.
For background, it is easier to compare if you have a peak to compare it against.
Re: GC-MS background keeps going up?
Posted: Thu May 30, 2013 11:50 am
by Don_Hilton
Rising background increasing over a number of GC runs is an indication of column contamination or degredation.
Some samples leave residues in the GC inlet that migrate the column and give increased background. Inlet maintanance and baking out the column can help witht his.
Running a column too long at or above the maxium operating temperature begins thermal degredation of the column. This only gets worse with time. And bakig nout the column does agrivates this problem.
Runnign poor quality carrier gas or with leaks allowing air to enter the the column will result in column degredation.
A bit more information on the history of the instrument might help get a more focused answer.