Pressure inconstance

<p>Hello,</p><p></p><p>used Acquity BSM; column = Spherisorb ODS 2, 150 x 2.1 mm, 3 µm</p><p>mobile Phase = 45 % MeOH / 55 % H2O</p><p></p><p>I have unusual high pressure inconstance (up to 6 bars between min and max). The inconstance is also visible in the chromatogram baseline.</p><p></p><p>See also the screen shots in the attachement.</p><p></p><p>What might be wrong?</p><p></p><p>PS. I purged each channel 20 minutes with water and MeOH; the problem is independent om the channels A1/A2 and B1/B2, respectively.</p><p></p><p>Thank you very much for each hint.</p><p></p><p>Florian</p>


  • This looks like an accumulator leak problem or some other malfunction with the accumulator.  The most frequent cause from what I've gathered with my limited experience is the valve seal is likely in need of replacing.  As your primary pump delivers to the accumulator, your accumulators pressure is spiking and then almost immediatly going back down- this is not how it should function.  It should "accumulate" pressure and retain it.

  • Hello,

    I have a few questions.

    1) Do you see this pressure delta with another column?

    2) What is your mixer volume?

    3) Have you performed a static decay test on the BSM?



  • Hello Michael,

    the phenomenon is independent on the column; static decay test failed. I had a waters engineer in-house. He replaced all the relevant parts of the pump and the phenomenon was still present. A change of the injection valve brought the solution.



  • My advice:  Perform the procedures and replace the parts that are included with the pump's Preventative Maintenance (PM) Kit.  Your local service engineer may be able to assist you in tracking down the offending check valve, piston, seal or connection and thus strategically remediate the problem.  However, a PM, while admittedly not inexpensive, is often the most expedient and thus cost effective.

    Good luck,


  • Hi,

    After the system was serviced, and you performed the chromatography and saw the issue was still persistant, have you performed another static decay test to confirm a passed test?


  • Hi Michael,

    after changing all pump parts, the static decay test has been performed and it failed.

    After change of the injection valve, it passed.



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