Uneven pressure in B pump

Question

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!

kbusch · Accepted Answer

Hey,

This looks as if one of the valves on channel B is sticking. This will cause this sort of pressure profile. The system pressure test cannot reach the target pressure because the valve is likely sticking and not closing properly. This symptom is normally a result of the acetonitrile polymerizing and resulting in polymers that stick to the ruby ***** in the valves. Sometimes the issue can be fixed simply by flushing the channel B with some water. If this doesn't help, I would recommend that you sonicate the valves on channel B. I find this article interesting about acn and check valves: http://www.chromatographyonline.com/check-valves-and-acetonitrile?id=&sk=&date=&pageID=3

Uneven pressure in B pump

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