Is Nitrite an interference for COD?
Nitrite interference in COD analysis
Hach does not provide a maximum interference level for Nitrite; high nitrite concentration samples are not within the scope of the COD testing method. However, nitrite has a theoretical oxygen demand of 1.1mg O2 per mg/L NO2. This interference should be eliminated by the addition of 10mg sulfamic acid per 1mg/L NO2. If you add the sulfamic acid it is recommended to analyze a separate blank containing the same concentration of sulfamic acid. High nitrite concentration samples are not within the scope of the COD testing method