This document specifies a method for the determination of nitrate as NO3-N in water of various origin 

such as natural water (including groundwater, surface water and bathing water), drinking water and 

wastewater, in a measuring range of concentration between 0,20 mg/l and 30 mg/l of NO3-N using the 

small-scale sealed tube method. Different measuring ranges of small-scale sealed tube methods can be 

required.

 The measuring ranges can vary depending on the type of the small-scale sealed tube method of different 

manufacturers.

 It is up to the user to choose the small-scale sealed tube test with the appropriate application range or 

to adapt samples with concentrations exceeding the measuring range of a test by preliminary dilution.

 NOTE 1 The results of a small-scale sealed tube test are most precise in the middle of the application range of 

the test.

 Manufacturers' small-scale sealed tube methods are based on chromotropic colour reaction, depending 

on the typical operating procedure of the small-scale sealed tube used, see Clause 9.

 NOTE 2 Laws, regulations or standards can require that the data is expressed as NO3 after conversion with 

the stoichiometric conversion factor 4,426 81 in Clause 11.

 NOTE 3 In the habitual language, use of sewage treatment and on the displays of automated sealed-tube test 

devices, NO3 without indication of the negative charge has become the common notation for the parameter 

nitrate and especially for the parameter nitrate-N. This notation is adopted in this document even though not 

being quite correct chemical nomenclature.