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Uneven pressure in B pump

Question asked by hcraigbarnes on Jan 15, 2020
Latest reply on Jan 20, 2020 by hcraigbarnes

I'm running a 1260 with a binary pump.

The method I'm currently running starts out at 60% B (Acetonitrile, A is water). As the gradient increases to 95% B over my run I'm seeing a very weird pressure profile (as can be seen in the attached chromatogram) and the pump makes a bit of a hiccuping ratcheting noise. 

I have tried a pressure test and the result has come back as ambiguous, with the suggestion of trying a valve test. I don't have a restriction capillary though, so can't do that yet.  Pressure test results also attached.

Any suggestions would be most welcome!