BÜCHI Labortechnik AG

TKN/Ammonia in Water & Wastewater by Steam Distillation


Courtesy of BÜCHI Labortechnik AG

The determination of total Kjeldahl Nitrogen (TKN) in water and waste water is a routine procedure used to ensure water quality. A simple and fast procedure for TKN determination as described in ISO 5663-1984, EPA 351.3, and AOAC 973.48 regulations, is introduced below. The sample is digested with sulfuric acid using the SpeedDigester K-436 or K-439, followed by distillation and titration with the Kjeldahl Sampler System K-370/K-371.


Total Kjeldahl Nitrogen (TKN) is a parameter for the evaluation of water and its pollution. The samples require digestion with sulfuric acid to convert nitrogen into ammonium sulfate. After conversion to ammonia through the alkalization with sodium hydroxide, the ammonia is distilled into a boric acid receiver via steam distillation, followed by a titration with sulfuric acid solution.  

This process follows:

CFR Title 40/Pt 136.3/31 Kjeldahl Nitrogen 5-Total,(as N), mg/l

Configurations can include Manual Digestion/Distillation/Titration or Block Digestion followed by AutoDistillation and Titration, See footnote 39...

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