Skip to main content

High pressure on ACQUITY H-Class QSM - WKB21450

Article number: 21450


  • Much higher pressure when pumping from C and D than from A and B with the same solvents
  • Pressure with A and B flowing is higher than normal
  • C is 100% water with no additives
  • Higher than expected back pressure or over pressuring during idle flow
  • Pressure spike to then over pressure during injection
  • Steady delta but over the course of 10 min or more a very slow pressure increase despite low delta




There is probably algae or some un-identified contaminant(s) in the system from the 100% water solution.


  1. Remove all solvents and solvent filters.
  2. Install new solvent filters and replace mobile phases with highest quality filtered 50:50 ACN:H2O
  3. Put all lines in fresh solvent.
  4. Remove column and install a union
  5. Extensively prime the whole system
  6. Set a flow and ensure appropriate system back pressure through union (system back pressure will vary depending on system configuration; e.g. H-Class Bio with QSM, SM-FTN, CM-A, and TUV should be around 1000 psi or less)
  7. Characterize the various system components pressures while flowing:
    1. Remove fitting at QSM inline filter outlet and record pressure
    2. Re-install QSM inline filter outlet and then remove connection at injector pod port 6, record system pressure (note that pressure up to port 6 is also dependent on whether the needle is part of the flow path, check by opening the sample manager door to see if the needle is in the middle of the compartment or seated in the inject station).
    3. Re-install port 6 fitting and then remove fittings along the flow path of the column compartment and record pressures.
    4. Also check the pressure of the flow cell by removing the fitting on the outlet of the flow cell as well as the back pressure regulator.
  8. If system continues to over pressure or pressure is excessively high during any of the sub steps from step 6, replace necessary tubing or parts and then perform step 6 again starting where the clog was found.
  9. Following successful system pressure characterization and any necessary part replacement, flush system over night with flow such as 0.5 mL/min.
  10. Check system pressure again compared to previous day to ensure the system is either performing the same or better.
  11. Install a new column to ensure system performance before installing old column that is suspected of being clogged.


Not able to find a solution? Click here to request help.