Fluorescence Detector Signal Not Balancing to Zero (OpenLab CDS)


Here is my setup:

  • OpenLab CDS version 3.6.2 with content management, local server
  • Fluorescence detector 1260 Infinity FLD (part number G1321C)
  • UV detector 1260 Infinity VWD (part number G1314B)
  • Binary pumps 1260 (part number G1312B)
  • CTC PAL injector

We have one single instrument configuration in OpenLab with both detectors in but we never use them at the same time, we simply untick "Acquire signal" from the detector we do not want to use.

The UV detector is the "access point" (plugged to the operating PC) and is working perfectly fine.

However for some odd reason the fluorescence detector signal never balances to zero, unless the lamp is switched off (see firsts part of the screenshot below).

When the lamp is switched on, there is a spike of signal followed by a quick equilibration to a value of about 0.3 LU.

When manually balancing the lamp (right-click > balance), the icon turns orange for a few seconds to indicate the balancing process.
When completed, it does not change anything for the signal, it remains close to 0.3 LU (see second part of the screenshot below).

The same result occurs when attempting to balance via the acquisition method:

In the Data Analysis window, the acquired chromatograms also do not start at zero:

Could it be that only the detector plugged to the operating PC (UV detector in my case) is allowed to balance the baseline?

Any suggestions to fix this?

Many thanks for your help!

  • Hello,

    This post may be more applicable to the HPLC forum, but I will ask have you tried to see if the FLD auto balance works in lab advisor?


  • Hello Martin,

    Thank you for the suggestion, we have the free version of Lab Advisor and it looks like there is no balancing control for both UV and Fluorescence detectors.

    I played a bit with the acquisition method settings (both under "Special Setpoints" and "Timetable") and I managed to have something close to what I want:

    Only with the weird combination of "Append" selected in the "Special Setpoints" and "Zero" in the "Timetable", somehow the baseline is balanced to 0 right before the start of the acquisition, probably one acquisition point prior.

    So there is still a tiny offset: by the time the first acquisition point is acquired, it's close to zero but not exactly zero, randomly higher or lower depending on the noise (with the UV detector it really starts at 0, as intended).

    And at the end of the acquisition, the signal goes back to around 0.3 LU until the next injection where it goes back close to 0 LU.

    In case anybody has another idea I'm still opened to suggestions, including for a way to manually balance the baseline.

  • Hello,

    I am going to move the post to the HPLC forum as they may have more information on the FLD detector behavior. 


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