The Total Kjeldahl Nitrogen (TKN) method quantitates the amount of nitrogen contained in organic form based on the wet oxidation of organic matter using sulfuric acid and digestion catalyst. The procedure converts organic nitrogen to the ammonium form. Ammonium is subsequently quantitated by the diffusion-conductivity technique (Carlson, 1978). The procedure does not quantitatively digest nitrogen from heterocyclic forms (bound in a carbon ring) or from oxidized forms such as nitrate and nitrite. The method has a detection limit of approximately 0.1 mg/L N.
Sample amount requested: 50 mL samples should be kept under refrigeration until analysis can be completed.
Questions concerning limited sample size can be answered by the UC Davis Analytical Laboratory.
EPA Method 351.2, Revision 2.0: Determination of Total Kjeldahl Nitrogen by Semi-Automated Colorimetry, August 1993
Carlson, R. M. 1978. Automated separation and conductimetric determination of ammonia and dissolved carbon dioxide. Anal. Chem. 50:1528-1531.
