Pressure Issues on UPLC

I am trying to figure out overpressurizing issues on this UPLC, and this is what the dashboard looks like. I am fairly new to UPLC (more experience with HPLC) but the QSM Primary pressure readout looks really strange to me. Is this typical for UPLC? Its currently 20% ACN/80% water in a Accq-tag 2.1x100mm column. 


  • Hi!  I hope that you have solved the issue by now but I thought I'd reach out just in case.

    It is a bit difficult to see the details in the screen capture, but it doesn't look too far from normal.  What you should see in the pressure traces (during equilibration or isocratic conditions) is a relatively solid line at system pressure on the Accumulator trace.  The primary fills the Accumulator, so you should see strokes that go from zero to system pressure in regular intervals based on the flow rate.  If you draw a line across the tops of the peaks on the primary, it should look identical to the Accumulator trace.

    If you see any deviation from this (difference in heights of primary strokes or drop-outs or wavy-ness in the accumulator) you might find some useful advice in this Troubleshooting guide on the Waters Knowledge Base