Page 1 of 1
GC-MS Baseline drift downward
Posted: Thu Mar 27, 2014 12:50 pm
by IdiotFool
Good morning, all.
I've got a Shimadzu QP-2010S unit with a column splitter to go to my MS and my FID. Recently, I did an overhaul on the whole system and replaced all column lines. When running samples and blanks, I'm seeing the MS baseline drift downward during a run. I do MS sweeps throughout the run, since I don't know what material I'm looking for and I don't want to miss anything by single ion monitoring. I'm currently running a blank of headspace air to see if it repeats, but I thought it might be a good idea to touch base with you all to see if you had any thoughts.
Thanks!
Re: GC-MS Baseline drift downward
Posted: Thu Mar 27, 2014 2:10 pm
by Peter Apps
Rule number 2 of trouble shooting; a problem that only occurs once is not a problem.
Peter
Re: GC-MS Baseline drift downward
Posted: Thu Mar 27, 2014 4:28 pm
by IdiotFool
Thanks, Peter. Unfortunately, this is happening continuously. Thoughts on a cause for a downward drift to baseline?
Re: GC-MS Baseline drift downward
Posted: Thu Mar 27, 2014 5:58 pm
by chemstation
How does your 207mz EIC look for column bleed.
How do you split your sample, eg two hole inlet ferrule, MicroFludic Splitter , Glass Y joint ,etc...
as more carrier gas may be getting in, diluting the ionization efficiency.
Have the relative responses changed on your test mixes or remained constant
from the early elutors to the last elutor, for both the MS and FID.
Alex
Re: GC-MS Baseline drift downward
Posted: Thu Mar 27, 2014 7:44 pm
by Peter Apps
Thanks, Peter. Unfortunately, this is happening continuously. Thoughts on a cause for a downward drift to baseline?
Very likely to be connected with changes in gas flows through the two detector lines as the oven temperature increase changes gas viscosity. The details of how to fix it will depend on the plumbing.
Peter
Re: GC-MS Baseline drift downward
Posted: Wed Apr 09, 2014 2:32 pm
by IdiotFool
Thanks, Peter. Unfortunately, this is happening continuously. Thoughts on a cause for a downward drift to baseline?
Very likely to be connected with changes in gas flows through the two detector lines as the oven temperature increase changes gas viscosity. The details of how to fix it will depend on the plumbing.
Peter
Turns out, it was just that I didn't give the mass spec enough time to stabilize. After a weekend, the baseline was flat and stable, with no issues observed during a run. I shouldn't have been surprised, since the machine was off for a month or so.