EN ISO 5983-2:2009

Foreword
1 Scope
2 Normative references
3 Terms and definitions
4 Principle
5 Reagents
6 Apparatus
7 Sampling
8 Preparation of test sample
9 Procedure
   9.1 General
   9.2 Test portion
   9.3 Determination
   9.4 Blank test
   9.5 Recovery tests
10 Calculation and expression of results
   10.1 Calculation
   10.2 Calculation of crude protein content
   10.3 Expression of crude protein content results
11 Precision
   11.1 Interlaboratory tests
   11.2 Repeatability
   11.3 Reproducibility
12 Test report
Annex A (informative) - Results of interlaboratory tests
Annex B (informative) - Results of a proficiency test; comparison
        of the colorimetric and potentiometric endpoint
        determination of the titration
Bibliography

ISO 5983-2:2009 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 is suitable for use as 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 % mass fraction 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.