NBN ISO 23697-2:2023

< p class=" MsoBodyText" style=" mso-layout-grid-align: none text-autospace: none " > < span lang=" EN-GB" style=" mso-bidi-font-size: 12.0pt " > This document specifies a method for the determination of total bound nitrogen (ST-TN< sub> b< / sub> ) in water of various origins: groundwater, surface water and wastewater, in a measuring range of concentration generally between 0,5 mg/ l and 150 mg/ l of ST-TN< sub> b< / sub> using the small-scale sealed tube method. Different measuring ranges of small-scale sealed tube methods can be required.< / span>

< p class=" MsoBodyText" style=" mso-layout-grid-align: none text-autospace: none " > < span lang=" EN-GB" style=" mso-bidi-font-size: 12.0pt " > The measuring ranges can vary depending on the type of small-scale sealed tube method of different manufacturers.< / span>

< p class=" MsoBodyText" style=" mso-layout-grid-align: none text-autospace: none " > < span lang=" EN-GB" style=" mso-bidi-font-size: 12.0pt " > 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.< / span>

< p class=" Note" style=" margin-bottom: 6.0pt tab-stops: 19.85pt 39.7pt 48.25pt 59.55pt 79.4pt 99.25pt 119.05pt 138.9pt 158.75pt 178.6pt 7.0cm mso-layout-grid-align: none text-autospace: none " > < span lang=" EN-GB" style=" mso-bidi-font-size: 12.0pt " > NOTE< span style=" mso-tab-count: 1 " >       < / span> The results of a small-scale sealed tube test are most precise in the middle of the application range of the test.< / span>

< p class=" MsoBodyText" style=" mso-layout-grid-align: none text-autospace: none " > < span lang=" EN-GB" style=" mso-bidi-font-size: 12.0pt " > All small-scale sealed tube methods are based on a heated alkaline potassium persulfate oxidation in a heating block at 100 °C and different digestion times are applicable. Chromotropic colour reaction is applied, depending on the typical operating procedure of the small-scale sealed tube used, see < span class=" citesec" > < span style=" color: black mso-color-alt: windowtext border: none " > < span style=" border: none " > Clause 9< / span> < / span> < / span> .< / span>