The USEPA Clean Water Act (CWA) requires national approval for all methods used for CWA compliance. There are approved methods for the determination of inorganic nitrogen (NO3-N, NO2-N, and NH3-N), and for organic nitrogen (TKN – NH3-N)2. There are no EPA approved methods for the determination of total nitrogen although it is a required parameter in many USEPA permits, including monitoring of nutrient pollution for ambient water criteria. Because Part 136.3 Table 1b methods are required, laboratories have no recourse but to measure total nitrogen as the sum of TKN, NO3-N and NO2-N 4 or as Simplified TKN (s-TKN™).
This paper introduces the new method: ASTM D8086-16, which compares favorably with the current EPA-approved calculated total nitrogen in samples without interferences. Utilizing the Shimadzu TOC-L total organic carbon analyzer with a total nitrogen module, ASTM D8083-16 saves laboratories time, uses less reagent and smaller sample volumes, and overcomes several known issues with current TKN and TN methods.