Method of determining urea in milk

Details Method of determining urea in milk Method of determining urea in milk

1992-05-19

1993-10-12

Hannaher, Constantine

Radiant energy

Invisible radiant energy responsive electric signalling

Infrared responsive

250343, G01N 3304, G01N 2135

Patent

active

052528294

ABSTRACT:
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, is determined with an accuracy better than 0.007%, expressed as Standard Error of Prediction, by an infrared attenuation measuring technique, by determining, on the sample, the attenuation in the region of infrared radiation from 1000 cm.sup.-1 (10.0 .mu.m) to 4000 cm.sup.-1 (2.50 .mu.m), at least one determination being made in a waveband in the region from 1000 cm.sup.-1 (10.0 .mu.m) to 1800 cm.sup.-1 (5.56 .mu.m) in which urea absorbs, at least one other determination being made in a waveband in which fat absorbs, at least one further determination being made in a waveband where lactose absorbs, and at least one further determination being made in a waveband where protein absorbs; determining, on the basis of the thus determined attenuations and predetermined parameters established by multivariate calibration, the contribution from fat, lactose, and protein in the waveband where urea absorbs, and 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 said waveband. The multivariate calibration may be performed by a Partial Least Squares algorithm, Principal Component Regression, Multiple Linear Regression, or Artificial Neural Network learning. Using the method according to the invention, compensation for the influence on the urea measurement may further be performed for one or several of the following components: citric acid, free fatty acids, antibiotics, phosphates, somatic cells, bacteria, preservatives and casein.

REFERENCES:
patent: 4169676 (1979-10-01), Kaiser
patent: 4447725 (1984-05-01), Biggs et al.
patent: 4663530 (1987-05-01), Shields
patent: 4855601 (1989-08-01), Savoyet
patent: 5017785 (1991-05-01), Rasanen
"Multivariate Calibration for Assays in Clinical Chemistry Using Attenuated Total Reflection Infrared Spectra of Human Blood Plasma", by G. Janatsch et al., Anal. Chem. 1989, 61, 2016-2023.
J. Clin. Chem. Clin. Biochem., vol. 26, 1988/No. 11, p. 749.
Clinical Chemistry, vol. 36, No. 2, 1990, pp. 401-402.
"The Composition of Milk: The Determination of Protein by the IR Method", Meijeritieteellinen Aikakauskirja XLI, No. 2, pp. 40-55, 1983.

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