Agilent 1100 pressure fluctuations only when using a mixture of solvents

Hi everyone,

I have been pressure fluctuations when mixing two solvents.  If either solvent is used 100%, I have no issues.  As soon as I attempt to use the system to automatically mix solvents, I experience pressure fluctuations. I am under the impression that this is the MCGV.  Is that correct?  Is there anything I can do, or is it a matter of replacing it?



  • Hi,

    It's not likely due to the MCGV.  When you are flowing 100% from each channel, you said there is no issue.  If it was the MCGV solenoid sticking or impeding the solvent flow somehow, you would experience pressure fluctuation.  It also cannot be due to the check valve or anything on the pump head as that is common to both channels.  What solvents were you trying to mix together?  Was it water and methanol?  That combination is exothermic and will outgas if there is no online degasser present.  

  • Hi,

    I was indeed trying to mix together water and methanol.  We have an online degasser in place, and I had previously attempted to manually pull out all traces of bubbles by hand.  Is there a way to test if the degasser is functioning properly?

  • Hi, 

    What's the model of the degasser?  If it's an Agilent and it's not functioning, the status light will be red.  The G1322A has 11ml in each chamber and should be sufficient to thoroughly degas while the G1379A/B has ~1ml.  For the G1379 degassers I have seen where the 2 channels are used for each solvent so the exit of water will go into the another channel before going to the pump.  You can try that if you have that model.

    One thing you can do is make sure you filter your solvent first by vacuum and in doing so, it will also begin the degassing process. 

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