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Noisy baseline on UV detectors - WKB933

Article number: 933


  • Noisy baseline
  • Reference energy higher than sample energy
  • Lamp has only 300 hours


  • 2487 Dual-Wavelength Absorbance Detector
  • 2489 UV/Vis Detector


Bad flowcell


  1. Replace the flowcell. See the user guide for the part number.
  2. Consult the user guide for information on flowcell cleaning.
  3. Refer to the appropriate user guide below:

2487 User Guide

2489 User Guide

2489 Overview Maintenance Guide


To measure the 2487 sample energy and reference energy, follow this procedure:

  1. Run 100% water through the flowcell, and then press "DIAG" on the detector front panel.
  2. Press 2, and then choose sample and reference energy using the up/down arrow. Press Enter.
  3. Set the wavelength to 230.
  4. Compare the two values; they should be similar and higher than 70.

If the reference energy is high compared with the sample energy, the flowcell may be dirty. If the sample energy is higher, it could be an issue with the photodiode or the front amplifier board. If they are both low, it is possibly the M1 mirror or the lamp housing window. If they are still low in value,it could be the M2/M3 or the grating.

Parts that are not listed in the Waters Graphical Parts Locator on the Waters website or in the user guide may need to be ordered or replaced by a Waters engineer.

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