ISO 5983-2:2005 specifies a method for the determination of nitrogen content of animal feeding stuffs according to the Kjeldahl method, and a method for the calculation of the crude protein content.
It concerns a semi-micro rapid routine method using block-digestion, copper catalyst and steam distillation into boric acid.
The method is applicable to the determination of greater than 0,5 % Kjeldahl nitrogen in animal feeding stuffs, pet foods and their raw materials.
The method does not measure oxidized forms of nitrogen nor heterocyclic nitrogen compounds. The method does not distinguish between protein nitrogen and non-protein nitrogen.