NEN 6646-1990 Water - Photometric determination of the content of ammonium nitrogen and of the sum of the contents of ammoniacal and organically bound nitrogen according to Kjeldahl by continuous flow analysis
The standard applies to the determination of dis olved ammonium in all types of water with an ammonium nitrogen content of at least 0.01 mg/l of N and to the determination of Kjeldahl nitrogen in all types of water with a Kjeldahl nitrogen content of at least 0.05. mg/l of N. Notes 1. Aromatic and heterocyclic nitrogen compounds are not fully determined. 2. Inorganic nitrate and nitrite as well as some metals can interfere with the determination of Kjeldahl nitrogen. 3. Some amines are also determined as ammonium, even after dis illation. 4. Dis illation is necessary if the sample for analysis is strongly colored and/or cloudy or if cloudiness occurs during color development.
NEN 6646-1990 history
1990NEN 6646-1990 Water - Photometric determination of the content of ammonium nitrogen and of the sum of the contents of ammoniacal and organically bound nitrogen according to Kjeldahl by continuous flow analysis