Metrohm NIRS XDS MasterLab Analyzer - Manual (Page 81)

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Vision plots the spectrum of the final
corrected reference spectrum in dark
green. This spectrum should appear
exactly the same as the calibrated
standard spectrum (red) which was
shown in the second screen. This view
also shows the unused wavelength area
on either side of that correction.
Vision notes that Reference
Standardization has been successfully
performed.
Click on “Print” or “Close Report”.
Please note that the instrument transmission reference is not calibrated to the spectral value of the
certified standard. It appears this way from the plot above, however, that is not the intention.
There is another mathematical step that is performed, but is not plotted. The correction file from the
dark green spectrum, which is the correction back to 0 absorbance (100% transmission) is also
applied. This brings the instrument reference back to a condition where it produces a true sample
spectrum, with no effect from the background characteristics of the instrument reference.
NOTE: Perform Reference Standardization immediately after changing the spot
size, to have the proper reference correction loaded in the instrument.
7.1.3 Instrument Calibration, Tablet Transmission
Instrument Calibration uses a stable,
wavelength standard, of known
wavelength response, as a method to
establish wavelength scale response of the
instrument. This wavelength standard is
directly traceable to NIST SRM-2035
through direct comparison on the
Metrohm NIRSystems master instrument.
The instrument scans the standard, and
the nominal peak positions (for each
major absorption) are determined. Vision
performs an algorithm to set the peak
positions of the instrument to those of the
standard.
These adjustments are saved, and are applied on each subsequent scan of the instrument, yielding a
correct spectrum.