The TN, or Total Nitrogen, Analyzer is an additional analysis tool available from BioTector Analytical Systems. When the BioTector oxidizes organic carbon compounds (for TOC measurement) it also oxidizes bound (organic and inorganic) nitrogen compounds and ammonium compounds into nitrate (NO3-). This nitrate is present as an aqueous ion in the oxidized sample fluid in the BioTector reactor. 
 
When TOC analysis is complete, the sample fluid is brought from the reactor into a measuring cell. Here a photometer analyzes the wavelengths applicable to nitrates. The result is displayed as Total Nitrogen (TN). A cleaning fluid is then passed through the measuring cell automatically, which ensures that operator cleaning and maintenance is kept to an absolute minimum.