Why does the color of the Holmium Oxide solution for HPLC performance Qualification look different than before - FAQ
October 12, 2017
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Date: 12-OCTOBER-2017   Last Updated: 5-JULY-2025

If you've noticed that the Holmium Oxide solution in your HPLC Qualification Kit or the  UV-vis Calibration kit appears to have a different color than you remember, there's no cause for concern. This is a normal and expected phenomenon due to the way the solution interacts with different types of ambient light.

Why the Color Appears to Change

Holmium oxide is a wavelength calibration standard, not a colorimetric standard. Its apparent color can vary significantly depending on the lighting conditions in your lab:
  • Under fluorescent lighting: The solution may appear bright pink or magenta
  • Under natural daylight or incandescent lighting: It often looks dull yellow or amber
This variation is due to the selective absorption and transmission of specific wavelengths of light. Holmium oxide has well-defined absorbance bands across the UV-Vis spectrum, which means it interacts differently with various light sources. What you're seeing is simply the result of spectral filtering—not a change in the chemical composition or quality of the solution.

Is the Solution Still Valid?

Yes. The color shift is purely visual and does not affect the performance or accuracy of the solution for wavelength calibration. As long as the solution is within its expiration date and has been stored properly (protected from contamination and excessive heat or light), it remains fully functional.
✅ No action is needed—your Holmium Oxide solution is still suitable for use in HPLC detector qualification.
📦 Click HERE for Holmium Oxide, PQ & HSQ Kit™ ordering information and images.
 

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