Metrohm NIRS XDS MasterLab Analyzer - Manual (Page 76)

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The directions that follow include spectroscopic
calibrations, which are used to “normalize” the
instrument, to minimize differences between
units of the same configuration.
The programs are accessed from the Diagnostics
menu bar, shown at right. The diagnostic steps
are explained in the sections that follow.
Vision uses a transmission instrument reference
that is similar in absorbance to tablets of medium
thickness. This assures that there is not a large
disparity between the reference and the sample
being measured, which enhances sample
reproducibility.
This reference is “Reference Standardized” on a
master instrument, to provide consistent readings
as if taken on air. Therefore, the MasterLab will
provide similar readings on like instruments.
Detector energy is highest between 850-
1600nm, as shown in this spectrum.
This is the spectrum of the tablet transmission reference without correction to an air reference. Vision
displays this as the reference, and applies the correction automatically to the data. All Performance
Test and Low Flux Test data are taken using this reference. Therefore, the noise values from these
tests are consistent with energy levels taken through typical tablets.
7.1.1 Wavelength Linearization, Tablet Transmission
Wavelength Linearization uses an internal wavelength material set to determine a set of internal,
arbitrary peak positions that the instrument will use to maintain repeatability of wavelength response.
The NIR wavelength spectrum
of the wavelength reference
materials, in transmission, is
shown. The scale is before
assignment of wavelengths,
and is “non-linear” data.
The area above “4800” is above
the usable range of the tablet
transmission detector, and is
ignored.