Metrohm NIRS XDS MasterLab Analyzer - Manual (Page 84)

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At the end of the test this dialog box is displayed. Print
confirmation of test results if needed for a log book or
other file.
Click “Print” to document the successful completion of
Instrument Calibration.
This is the report from Vision to
document completion.
Click “OK” to exit Instrument
Calibration.
During Instrument Calibration, the wavelength response for each defined peak is adjusted, to assure
precise wavelength registration between instruments. At the same time, bandwidth (bandpass) is
measured, and is iteratively adjusted to an optimum value for the areas measured. This is performed
to assure good agreement from instrument to instrument, should multiple instruments be used for
analysis of similar products.
Information about the Tablet Transmission Wavelength Standard:
The Tablet Transmission Wavelength Standard used is directly traceable to NIST SRM-2035, through
direct comparison on the Metrohm Master Transmission instrument. The rare-earth glass used
contains many of the same rare earth materials as SRM-2035, and the resulting peaks therefore
appear in the correct locations when compared to SRM-2035.
Because tablets are a light-scattering medium, a scattering transmission wavelength standard is used.
In addition, the relative absorbance level of the wavelength standard is formulated to be close to that
of tablets, without losing the sharp wavelength peaks that are used to define correct wavelength
positions. Rare-earth glasses are sandwiched with a neutral absorber to reach the level of absorbance
required, without affecting wavelength position. By constructing a wavelength standard of medium
absorbance, the user is assured that tablet wavelength positions (of similar absorbance levels) will be
located correctly on the wavelength axis.
Spectra of each are as described:
The spectrum at the top is NIST SRM-2035, with neutral density filters (which impart no wavelength
shift) added to reach absorbance levels close to that of the FOSS NIRSystems wavelength calibration
standard.
The FOSS WST Wavelength Calibration Standard is the darker spectrum, just below SRM-2035. Note
that the positions of key peaks are marked with a vertical line, to show clear correlation to SRM-2035
peaks. Some of these peaks are used to set the wavelength scale of the instrument to aid in
instrument matching. This is one important step in method transfer.
The bottom spectrum is NIST SRM-2035 with no neutral density filters added. This spectrum is shown