Weird Baseline Disturbance

Has anyone ever encountered this type of baseline disturbance? I just had a PM performed my the instrument (7890B GC, 7200 QTOF and 8355 SCD) and they installed a nitrogen tank to the collision cell.

Any ideas what could be causing it?

  • We need more information to be helpful....

    Is that the 7200 TIC or the 8355 signal?    The 7200 needs typically 1.5 ml/min of N2 flow into the collision cell for best sensitivity. Was it not there before?

    Is the required electronics purge flowing into the 7200?  Are all the gas pressures high enough to support the required flows?   All gas flow controls need at least 20psi higher than the required pressure for decent flow control. So if the inlet needs, say, 25psi then the supply needs to be at least 45psi or higher.

  • It is the 7200 signal and the N2 flow has always been set at 1.5ml/min so not change there. 

    I’ll check all the gas flow pressures. 

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