TKN is the total concentration of organic nitrogen and ammonia. The original TKN method was developed by the Danish chemist Johan Kjeldahl in 1883. Today, TKN is a required parameter for regulatory reporting at many plants but is also used to provide a means of monitoring plant operations.
The traditional TKN method consists of digesting the sample at high temperatures for several hours with strong sulfuric acid and metal catalysts such as copper or mercury. Ultimately, the organic nitrogen is converted to ammonia for determination by a variety of analytical techniques. The analysis requires expensive, fragile equipment along with a large amount of laboratory space. In addition to the above limitations, the TKN method suffers from interferences that are not well understood and traditional methodologies have been unable to correct for these.