Metrohm NIRS XDS MultiVial Analyzer - Manual (Page 62)

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The results screen shown above is typical. Peak positions for the reference materials are located using
a peak-finding algorithm. These “found” peaks are compared to the nominals. Differences should be
no more than 0.4nm for any peak. Click “Yes” to send the linearization to the instrument.
After the linearization is successfully sent to the instrument,
this message confirms the transfer.
Click “OK” to proceed. This is run in each direction of grating
motion. Continue until finished.
7.1.2 Reference Standardization, “Use Tray” Position
Reference Standardization is a method to provide a virtual 100% reflectance reference at each data
point, to serve as a true spectroscopic reference with no character attributable to the physical
reference used. This is important to achieve a high-quality spectrum on each instrument, and to
enhance transferability between instruments.
A photometric standard of known reflectivity (as measured on an absolute reflectance scale) is
scanned on the instrument. The internal ceramic standard is scanned. The differences of the ceramic
standard from 100% reflectivity are mapped, and a photometric correction is generated. This
correction is then applied to every spectrum taken on the instrument, to make each spectrum appear
as if taken with a reference of 100% reflectance. This assures that bright samples do not saturate the
instrument, or produce negative absorbance values.
The MultiVial Analyzer requires two reference standardizations, one for each sampling
level.
The first level is with a vial directly on the sample window, in “Use Iris” mode, with the Iris Adapter.
The second level involves the MultiVial tray, in “Use Tray” mode, where the vial tray is slightly above
the sample window. Vision applies the correct Reference Standardization based upon selection of
“Use Iris” or “Use Tray” in the Configure, Tray menu.
To account for the difference in sampling height, the background reference is adjusted using
Reference Standardization. The benefit of this system is that only one calibration (or library) is
required, and serves both sampling levels. (Without this system, two sets of calibrations [or libraries]
would be required for operation.)
To repeat: Vision software stores the two Reference Standardization files, which are downloaded to
the instrument, and are applied as a correction to each spectrum. (Vision knows which file to use
based upon selection of the “Use Iris” or “Use Tray” in the Tray dialog box.)
NOTE: In the event that Vision does
not find a Reference Standardization
where it is needed, it will prompt for a
new one upon connection as shown.
When a new Reference Standardization
is performed, Vision may ask for a new
Instrument Calibration as well.
Follow these steps to create a reference standard. The instructions are shown for the “Use Tray”
position. Upon completion of these steps, select the “Use Iris” position and perform a Reference