2695 Separations Module 2489 UV/Vis Detector: The baseline keeps dropping - WKB93441

SYMPTOMS

• It is seen that the baseline drifts downward during equilibration for some time, but it becomes straight after equilibrating for 2 to 30 minutes.
• Recently, the baseline drifts downward all the time even wait longer, and if start the run, peaks are detected at the baseline which drifts downward.
• Used multiple types of mobile phases, the same trend was seen
• Used multiple types of columns, the same trend was seen
• The baseline is straight with 2475 detector, it drifts downward only with the 2489 detector.
• The pressure fluctuation about Δpsi hasn't been confirmed, but there is no rising or droping just as usual.

ENVIRONMENT

• 2695 Separations Module
• 2489 UV/Vis Detector
• 2475 Multi-Wavelength Fluorescence Detector

CAUSE

Decrease in lamp energy (contamination in the cell)

FIX or WORKAROUND

1. Check the lamp energy (see ADDITIONAL INFORMATION for details)
   If the sample energy is less than half the reference energy, there may be a problem.
2. Check the lamp hours, and if it has not been replaced for a while, replace it.
3. Cleaning the detector cell
   1.Prepare the washing solvents (three of water, acetonitrile : isopropanol = 1: 1, and 30% phosphoric acid)
   2. Add the washing solvents into sample vials
   3. Remove the column and connect the tube in front of the 2695 column and the tube at the detector inlet with a union (connect only the 2489 detector if cleaning of the 2475 detector is not required).
   4. Remove the solvent filter
   5. Prime all lines except the seal wash line with the washing solvents.
   6. Create the instrument method used for cleaning Flow rate: 0.5 mL/min
   7. Create the sample set used for cleaning
   Injection volume: Needle capacity
   Run time: 0.1 min
   Number of injections: 30
   * *For the above cleaning, first wash with water for 1 hour, then acetonitrile : isopropanol = 1:1 for 3 hours, then 30% phosphoric acid for 3 hours, and then water for half a day (specified time is a reference).
   * The cleaning solvent is listed, but if there is a solvent that dissolves the sample more easily, wash it with that solvent.
   * Cleaning of the injection part is also included, but if it is not necessary, there is no problem just by flowing the cleaning solvent.
4. Rebuild the cell or replace the cell (please contact Waters)

ADDITIONAL INFORMATION

■Confirming the lamp energy

Noisy baseline on UV detectors - WKB933

■ Lamp energy value of 2489 detector before cleaning procedures above
sample 26.380
ref 269.375

■ Lamp energy value of 2489 detector after the cleaning procedures above
sample: 203.485
ref: 267.085

* The above energy values are just examples and may differ depending on the condition of the instrument. Please use it as a reference only.