Metrohm NIRS XDS Process Analyzer – DirectLight/NonContact - Manual (Page 116)

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At the end of the test this dialog box is displayed.
Click “OK” to exit Instrument Calibration.
Information about the Reflectance Wavelength Standard:
The reflectance wavelength standard used is directly traceable to NIST SRM-1920a, through direct
comparison on the Metrohm Master Reflectance Instrument, and in chemical formulation.
In addition to the prescribed formulation, one additional ingredient is added, in a small amount, to
provide peaks beyond those normally found in SRM-1920a. This material has very sharp bands, which
are found to be stable and repeatable.
Spectra of each are as described:
The darker spectrum, which has no discernible peaks beyond about 2150nm, is SRM-1920a.
The Metrohm WSR Wavelength Standard is the lighter spectrum, and has clear peaks visible at above
2200nm.
These additional peaks are used to set the wavelength scale of the instrument to aid in instrument
matching. This is one important step in calibration transfer.
The Metrohm WSR Wavelength Standard exhibits slightly different absorbance and baseline levels,
due to the reflectivity of the added ingredient. The peaks, however, are in the same wavelength
positions, and are similar in shape to SRM-1920a.
In Instrument Calibration, the XDS instrument is set to nominals which provide excellent instrument
transfer, and which meet published NIST wavelengths when tested in Wavelength Certification. Peaks
for the additional ingredient are set to peak nominals determined by measurement on several
different types of research instrumentation.
In Wavelength Certification, the NIST-stated uncertainty of 1.0nm is applied. Tighter tolerances are
not appropriate, unless NIST revises the stated uncertainty of SRM-1920a at some point in the future.