DIN 10484:2013-09

This standard specifies a photometric method for the determination of urea and ammonia in milk. As the determination of urea contains the formation of ammonia it is necessary to measure and to take into account the amount of ammonia already present in the sample. The method is applicable on raw milk, market milk and reconstituted milk. In the presence of the enzyme urease urea is split into ammonia and carbon dioxide. When in the presence of glutamate dehydrogenase (GLDH) enzyme and reduced nicotinamide adenine dinucleotide (NADH), the formed as well as existing ammonia changes 2-oxo-glutarate to L-glutamate. The amount of NADH used during the reaction is equivalent to the amount of ammonia as well as half of the amount of urea. The parameter here is NADH, which due to its absorbance at 340 nm is spectrophotometrically definable. DIN 10484 has been prepared based on the AFNOR standard NF V 04-217:1992-12. This standard describes an alternative measurement method to DIN EN ISO 14637 "Milk - Determination of urea content - Enzymatic method using difference in pH (Reference method)". The committee responsible for this standard is NA 057-05-13 AA "Milch und Milchprodukte - Probenahme- und Untersuchungsverfahren" ("Milk and milk products - Methods of sampling and analysis") at DIN.