Metrohm NIRS XDS Process Analyzer – MicroBundle - Manual (Page 80)

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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 FOSS 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 FOSS 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.
10.3.4 Window Correction, Interactance Immersion
Window Correction is a method to permit the user to calibrate the fiber optics using an Interactance
Reflectance Probe, then insert the fiber into the Interactance Immersion Probe, and map the optical
difference in response between the two geometries.