The method applies to sludge, such as sewage sludge, sediments and suspended substances in wastewater or surface water. Aromatic and heterocyclic nitrogen compounds are not fully determined. Inorganic nitrate and nitrite as well as some metals can interfere with the determination (see 7.3).
NEN 6641-1983 history
1983NEN 6641-1983 Sludge - Determination of the sum of ammoniacal and organically bound nitrogen according to Kjeldahl after mineralization with selenium