Increase in noise/bleed after changing carrier gas scrubber

After changing the O2/H2O scrubber on our 5977/8890 we experienced a large increase in noise/column bleed.  I did check the air/water levels about an hour after the scrubber change, and the levels were ~3% for water and nitrogen. 

After running a blank sample the baseline noise increased by more than 60-fold.  No other changes to the instrument or method were made.  I know the scrubbers are packed under nitrogen, but I thought it had mostly moved through the system. 

Since then I worked with our FSE on cleaning the HED and source.  I have tuned and retuned several times.  I restored the ATune and BFB files from the 5977.old folder without any improvement in noise/bleed.

This system is used for TO-15 analysis and has a preconcentrator attached for CTD.

Any ideas?

Thank you.


  • Which O2/H2O filter did you change?  The Agilent GasClean carrier gas cartridges are shipped filled with Nitrogen and purging that out can take some time depending on your inlet flow rate settings.  I set the inlet to split, column flow about 0.2 ml/min - inlet pressure 2psi or so, then split flow at 400 ml/min for ten to fifteen minutes.  Then reset to your normal operating parameters, wait five or ten minutes for stability, and tune.

    Baseline noise is inexact. What noise? What ions are making up the noise? What's your scan range?  Did the EM voltage change from before to after?  Can you share a current tune report?  Can you share a spectrum of the noise?  You may need to change your scan range and lower the start to 10 amu so that you can see any water or air in the signal. 

  • Hi Paul,

    Ions we are seeing are siloxanes (column bleed, DB-1 column).  We scan from 35-350 amu.  We do have water peaks from the preconcentrator injection, but the amount of water noise increased.  I have tweaked some tune settings (gain factor especially) and the noise has come down significantly, however the bleed near the end of the run is quite a bit higher than usual.

Was this helpful?