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Increasing system pressure leads to over-pressure shutdown with Alliance system - WKB10227

Article number: 10227


  • Over-pressure shutdown, and chromatography looked different
    • Negative sloping baseline affects peak integration.
    • Higher than normal pressure readings
  • Initial conditions are 50:50 water/acetonitrile. 
    • Gradient composition increases to 100% acetonitrile 
  • Overlays of pressure traces do not match from run to run
    • Higher pressure at 100% acetonitrile
  • Pressure behaves correctly with a new column, but then increases slowly over time
  • Static leak diagnostic and compression test are successful


  • 2695 Separations Module


Microbial contamination in the system may be responsible for higher pressure as gradient composition changes toward higher organic.

Contamination builds up on new columns over time, leading to high pressure and over-pressure shutdown.


  1. Remove the column and run a waste line directly to a waste container.
  2. Clean, flush, or passivate all lines in the Alliance system with 6N nitric acid.
    • Note: Prior to and following cleaning, flush the system with water to set the pH and neutralize the waste at the outlet to waste.
  3. Replace solvent filters and in-line filters.
  4. Replace solvents; add fresh mobile phases with new bottles.



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