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1. (WO1993019364) PROCEDE DE DETERMINATION DE LA CONCENTRATION D'UREE DANS DU LAIT
Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

CLAIMS

1. A method for determining, with an accuracy better than 0.007%, expressed as Standard Error of Prediction, the concentration of urea in a concentration range of 0-0.1% in a milk sample containing at least 1% fat, at least 1% dissolved lactose, and at least 1% protein, by an infrared absorption measuring technique, said method comprising the steps of:
(a) determining absorption in an infrared radiation
waveband from 1000 cm-1 (10.0 μm) to 4000 cm"1 (2.50 μm) of the milk sample, at least one determination being made in a waveband from 1000 cm"1 (10.0 μm) to 1800 cm"1 (5.56 μm) in which urea absorbs, at least one determination being made in a waveband in which fat absorbs, at least one deter-mination being made in a waveband where lactose absorbs, and at least one determination being made in a waveband where protein absorbs;
(b) determining, on the basis of the absorption
determinations and predetermined parameters established by multivariate calibration, a contribution from fat, lactose, and protein in the waveband where urea absorbs, and
(c) quantitatively assessing the concentration of urea in the sample on the basis of the absorption in the waveband where urea absorbs and on the basis of the determined contribution from fat, lactose, and protein in the
waveband.

2. A method according to claim 1, wherein the predetermined parameters established by multivariate calibration are obtained using milk samples containing known concentrations of urea, or milk samples to which known concentrations of urea have been added.

3. A method according to claim 1 or 2, wherein more than one determination is made in the wavebands where urea, fat, lactose, and protein absorb.

4. A method according to any of the preceding claims, in which, in addition to urea, also the concentration of the components fat, lactose, and protein is calculated (predicted) , each determination being based on at least one measurement in a waveband at which the component in
question absorbs.

5. A method according to any of the preceding claims, wherein the multivariate calibration has been made using milk samples containing known concentrations of urea, fat, lactose, and protein, and/or milk samples to which known concentrations of urea, fat, lactose, and/or protein, have been added, and/or the physical conditions (temperature, degree of homogenization) of which have been modified.

6. A method according to any of the preceding claims, wherein the multivariate calibration has been performed using at least 4 milk samples.

7. A method according to claim 6, wherein the multivariate calibration has been performed using at least 8 milk samples.

8. A method according to claim 7, wherein the multivariate calibration has been performed using at least 12 milk samples.

9. A method according to claim 8, wherein the multivariate calibration has been performed using at least 18 milk samples.

10. A method according to claim 9, wherein the multivariate calibration has been performed using at least 25 milk samples.

11. A method according to any of the preceding claims, wherein the Standard Error of Prediction (SEP) is better than 0.005%.

12. A method according to claim 11, wherein the Standard Error of Prediction (SEP) is better than 0.004%.

13. A method according to any of the preceding claims, wherein the region in which the determination of urea is made is the region of 1100 cm"1 (9.09 μm) to 1800 cm"1 (5.56 μm) .

14. A method according to any of the preceding claims, wherein the region in which the determination of urea is made is the region of 1400 cm-1 (7.14 μm) to 1500 cm"1 (6.67 μm) .

15. A method according to any of claims 1-13, wherein the region in which the determination of urea is made is the region of 1500 cm"1 (6.67 μm) to 1800 cm"1 (5.56 μm) .

16. A method according to any of claims 1-13, wherein the region in which the determination of urea is made is the region of 1100 cm"1 (9.09 μm) to 1200 cm"1 (8.33 μm) .

17. A method according to any of the preceding claims, wherein the absorption determinations are performed in wavebands defined by optical filters.

18. A method according to any of claims 1-16, wherein the absorption determinations are performed in wavebands defined by a stationary grating and movable and/or multiple detectors or by a movable grating and one or several stationary or movable detectors.

19. A method according to any of claims 1-16, wherein the absorption determinations are performed over a broad spectrum range using an interferometer and the data
obtained from the interferometer is processed using Fourier transformation.

20. A method according to any of the preceding claims, wherein the absorption determinations are performed using an ATR technique.

21. A method according to any of claims 1-19, wherein the absorption determinations are performed using a
transmission technique.

22. A method according to claim 21, wherein the infrared light is transmitted through a cuvette containing the milk sample, the path length of the cuvette being at most
200 μm.

23. A method according to claim 22, wherein the infrared light is transmitted through a cuvette containing the milk sample, the path length of the cuvette being at most 50 μm.

24. A method according to any of the preceding claims, wherein the multivariate calibration is performed by a method selected from the group consisting of Partial Least Squares algorithm, Principal Component Regression, Multiple Linear Regression, and Artificial Neural Network learning.

25. A method according to any of the preceding claims, wherein any fat globules in the milk sample have a mean diameter of at most 3 μm.

26. A method according to any of the preceding claims, wherein compensation for influence on urea measurement is further performed for one or several of the following components: citric acid, free fatty acids, antibiotics, phosphates, somatic cells, bacteria, preservatives and casein, by performing, for each component, a determination of infrared absorption in a waveband in which the component absorbs, the compensation being performed on the basis of multivariate calibration by combining the results, for all components for which compensation is to be made, from the determinations made in the wavebands where the components absorb.