pressure drop and high ripple


I have an Agilent 1260 Infinity II system with an isocratic pump, UV-vis and RI detector. After purging the system and equilibrating the column, there is a high pressure ripple that slowly tapers down to normal pressure and ripple. However, seemingly at random, the pressure will suddenly drop by about 10 bar and the large ripple will return, before once again equilibrating to normalcy. I have attached a picture of what I am trying to convey, but please excuse the phone picture, as the computer is not connected to any network. The red line is the pressure line.

For what has changed recently, this is a new 250 x 4.6, 5um c18 column, and yearly PM was just completed on the machine two weeks ago. I would like to know the opinion of the experts here before I start my own investigation by changing the column, bypassing the valve switch port and/or degasser, and/or replacing any lines. Please and thank you!

  • Hello CRishel,

    That looks like a check valve issue.  The drop can be a result of an air bubble getting into the system and then experiencing a "air lock".  If you purge the system and it goes back to normal, then yes, it was most likely air.  It can also be as a result of particles getting into the check valves.  Make sure the solvent bottle is clean, there isn't anything floating in it and always a good practice to filter mobile through a 0.45u filter before using.

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