1. Construction of a calibration model stable to structural changes in a grain analyzer P.A. Luzanov, K.A.Zharinov, V.A.Zubkov LUMEX Ltd., St. Petersburg, Russia

2. The InfraLUM FT-10 analyzer optical diagram 1. Radiation source unit 5. Sampler 2. Interferometer 6. Cell with a sample 3. Optical unit 7. Photodetector 4. Cell compartment

3. Calibration equation y=X T *p+e y is the vector of the reference values of dimension n, n is the number of spectra included in the calibration; X T is the transpose of the matrix of the spectral data of dimension f by n, f being the number of the discrete wavenumbers at which the spectra were measured; p is the calibration factors vector of dimension f; and e is the error vector of dimension n.

4. Calibration of the instrument - protein wheat properties the ranges of reference values 10.5-15.7% 15.1-26.2%- gluten

5. Calibration of the instrument Results of verification of the initial calibrations on the instrument with different beamsplitters by validation using additional set of samples

6. Algorithm of calibration model correction, step 1  Selection a calibration set of samples  Registration their spectra on an instrument  Construction a PLS calibration model allowing for the current condition of the analyzer

7. Algorithm of calibration model correction, step 2 Selection a set of representative samples from the calibration set of samples with the maximum and minimum values of the score parameter for each of the analyzed properties

8. Algorithm of calibration model correction, step 3 Changes are artificially introduced in the design features of the instrument, which lead to the largest deviation of the analysis results from the initial calibration model

9. Algorithm of calibration model correction, step 4 Registration the transmittance spectra of the selected samples on the instrument with the changes introduced in its design features

10. Algorithm of calibration model correction, step 5 Construction a PLS calibration model using the spectra of the calibration samples recorded on the original instrument and the spectra of the samples from the selected set recorded on the instrument with changes introduced in its design features

11. Comparison of calibrations Initial calibrations Calibrations corrected allowing for the replacement of the beamsplitter

12. Verification of calibrations on the instrument with different beamsplitters Initial calibrations Calibrations corrected allowing for the replacement of the beamsplitter

13. Conclusions The study of various structural components of the instrument under investigation and the extent of their influence on variation in calibration and, accordingly, on the quality of the analysis, has demonstrated that one of the main affecting factors is the beamsplitter ; The obtained experimental data have confirmed the operability of the algorithm used for constructing a calibration model that is stable to a change in the performance characteristics of the instrument due to its ageing, repair, replacement, or readjustment of any of its units.