BUCHI NIRCal User Manual
Page 167
Chemometrics
NIRCal 5.5 Manual, Version A
167
In case the predicted and original properties are different, it is a wrong identification: spectra 73-77
and 83. These spectra are in a false cluster, but will not be identified, while the residuals are much
higher (0.0042) as the allowed residual (0.0002).
Correct identifications -case 3- and not identified unknown -case 7- are less important, deactivating
e.g. case 3 and 7 will give a shorter protocol.
Especially cases 1 and 5 are critical. By case 5 the residual relationship (actual against allowed)
should be controlled. Case 2 is inacceptable.
In summary all spectra should be listed under the number of “Total identified” or “Total not identified
unknown”, no spectra should be in the 5 other types. Printouts of the prediction protocols are part of
the validation procedure.
When the result is unsatisfactory, the calibration adjustment should be changed.
In case there is no any calibration, which problems without works, the possibilities of improvement are:
not in a Cluster
(!)
Add these spectra to the project without allocating them to C- or V-Set.
Calculate and observe if the spectra are lying far from the cluster. If not, the
spectra must remain in the project (similar spectra)
false identified
(?)
Add the spectrum that was identified as false to the project and enlarge the
calculation (similar spectra)
identified (*)
The spectra are OK (known, identified)
not identified
Clu OK (%)
These spectra are rare, because the known substance spectra are only to be
found in one project, eventually add such spectra to the C-Set.
not identified
Clu BAD (&)
Reducing the Radii Blow Up Factor may help. Otherwise compare max allowed
residual with actual residual. When the actual one is 150% or more than the
allowed, the calibration can be used. In case the actual residual is slightly
higher than the allowed, the spectra should be calibrated in the same project.
not identified
known (-)
These spectra are rare because the known substance spectra are only to be
found in one project, eventually add these to the C-Set.
not identified
unknown (=)
The spectra are OK (unknown, not identified).
Only calibrations without false identification can be used.