BUCHI NIRCal - Manual (Page 13)

Introduction
NIRCal 5.5 Manual, Version A 13
Figure.1: Solvent spectra (acetone, ethanol, toluene and dichlor-methane), measured through
glass cuvettes with measurement option liquid. The slight shifts (light scattering) are not of interest
and should be reduced with data pretreatments.
Figure.2: Spectra out of figure 1 after data pretreatment (here: 1st derivation)
Systematic differences of the four solvents are clear and reproducible
For the actual calibration, the Cluster calibration using PCA has been used. This means a calculation
of a new illustration of the spectral information with the target to show the main differences in the data
set. Spectra appear after the calculation in the new illustration as points in a 2D or 3D Plot.*
The calculation can be performed automatically by the Calibration Wizard. According to the required
input by the Wizard concerning measurement method and dedicated calibration type, different
calibrations are calculated and sorted by a specific quality attribute (Q-Value). For an optimal result,
the wavelength selection, the data pretreatments and the optimal number of PCs must be chosen
adequately. This is automatically done by the software.
Good qualitative calibrations can be recognised as the single spectra are found in well separated
tolerance regions -Clusters- where each represent only one of the possible categories (properties).