Development of ISO Standards for the Determination of Ammonia, Nitrate and Total Nitrogen Using Tube Tests

Collaborative Efforts to Improve Environmental Monitoring (Session 2)
Oral Presentation

Prepared by C. Prokisch
MACHEREY-NAGEL, Valencienner Strasse 11, Dueren, NRW, 52355, Germany

Contact Information: [email protected]; 020-421-9690


“Nutrient pollution is one of America´s most widespread, costly and challenging environmental problems” (as seen on Nitrogen is an important nutrient and tube tests are widely used to control nitrogen removal processes on sewage plants. Three ISO-projects lead by Italy seek to standardize tube tests for ammonium, nitrate and total nitrogen.
ISO DIS 23695 describes the photometric ammonium test that is based on the principle of the Berthelot reaction, which develops an indophenol blue color. The test is very easy; however, care needs to be taken, that the reagents are at room temperature when used.
ISO DIS 23696 is for the detection of nitrate and currently has two parts. Part 1 deals with the reaction with dimethylphenol (DMP) while part 2 describes the reaction with chromotropic acid. Both tests are reliable and easy and have been on the market from different manufacturers for many years.
ISO DIS 23697 does also come with two parts. These, however, do only reflect the two different ways in which nitrate is detected after digestion (see ISO DIS 23696). The digestion part itself is identical in both documents: the sample is heated in strongly alkaline solution with potassium persulfate, which oxidizes organic and inorganic nitrogen to nitrate.
Professional wastewater analysts as well as chemical laymen appreciate the reliability and ease of use of tube tests. For many years, such tests have already been available from a variety of manufacturers, among them MACHEREY-NAGEL, the employer of the author. MACHEREY-NAGEL is a German company founded in 1911 that is the major competitor of HACH in Germany and large parts of Europe.