Samarium perchlorate is a particularly useful reference material for checking the wavelength scale over the commonly used region from 200 nm to 500 nm.
It is accepted for this purpose by several Pharmacopoeias and Standardisation Bodies, including:
United States Pharmacopeia
American Society for Testing and Materials
Therapeutic Goods Administration (Australia)
Description and Discussion
Rare earth oxide in sulfuric acid, permanently sealed by heat Samarium (III) oxide in dilute perchloric acid, permanently sealed by heat fusion into a 10 mm far UV quartz cuvette.
Samarium perchlorate is a particularly suitable reference material for checking the wavelength scale of a spectrophotometer over the commonly used range of 200 to 500 nm, as it has peaks throughout this region. Many of the peaks are very narrow, providing very accurate location of the peak wavelengths.
Approximate peak wavelength values (in nm) are:
235, 279, 290, 305, 318, 332, 344, 362, 374, 391, 401, 415, 464, 479
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 Samarium 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 only these certified values should be used for instrument qualification. On request, Starna can provide certifiedvalues at other wavelengths and bandwidth values.
The narrow peaks in the Samarium spectrum give accurate peak location, but users should be aware of the effect of instrument bandwidth on the measured peak wavelength. With a half band width of as little as 5 nm, some peaks provide a useful indication of instrument resolution. The scan below of the peaks at 233/235 nm illustrates this effect.
The ability of a given spectrophotometer to resolve the firstand second order satellite peaks on the sides of the main peak is related to the spectral bandwidth.
Samarium Oxide liquid cell