This Reference Material can be used to qualify the wavelength calibration, in the ultraviolet and visible regions of the spectrum (240 nm - 650 nm*) of spectrophotometers with spectral bandwidths of (SBW) 5 nm or less. It is accepted for this purpose by most Pharmacopoeias and Standardisation Bodies, including:

European Pharmacopoeia
Deutsches Arzneibuch (German Pharmacopoeia).
United States Pharmacopeia
American Society for Testing and Materials
Therapeutic Goods Administration (Australia)
British Pharmacopoeia

*This range can be extended to 200 nm - 650 nm for instruments with 1 nm SBW or less


Description and Discussion

Holmium oxide (4% m/v) in 10% v/v perchloric acid, permanently sealed by heat fusion into a 10 mm far UV quartz cuvette.

The use of holmium oxide solvated in perchloric acid is an established and well recognised method for the validation of the wavelength scale of a spectrophotometer in the UV and visible regions. Aqueous perchloric acid solvent is used as the solvent as the resulting Ho3+aq species is relatively stable to changes in temperature and concentration.

When prepared in perchloric acid, holmium oxide gives a spectral scan containing a series of 14 characteristic andwell-defined peaks covering the wavelength range from 240to 650 nm.

Typical spectra


Approximate peak wavelength values (in nm) are:
208*, 219*, 233*, 241, 250, 278, 288, 334, 346, 361, 385, 417, 451, 468, 485, 537, 641 (*Available upon request)

Note: The above values are for guidance only. Because the absorption bands are asymmetric, measured values will bespectral bandwidth dependent. The Calibration Certificate accompanying each Starna Holmium reference gives actual values measured at bandwidths of 0.10, 0.25, 0.50, 1.00, 1.50, 2.00, 3.00, 4.00 and 5.00 nm, and onlythese certified values should be used for instrument qualification. On request, Starna can provide certifiedvalues at other wavelengths and bandwidth values.


Catalogue Number

  Catalogue  Number

Holmium oxide liquid cell