YBOTECH Kjeldahl System: The Kjeldahl method or Kjeldahl digestion in analytical chemistry is a method for the quantitative determination of nitrogen contained in organic substances plus the nitrogen contained in the inorganic compounds ammonia and ammonium (NH3/NH4+). Without modification, other forms of inorganic nitrogen, for instance, nitrate, are not included in this measurement.

Using an empirical relation between Kjeldahl nitrogen content and protein content is an important method for analyzing proteins. This method was developed by Johan Kjeldahl in 1883. The Kjeldahl method’s universality, precision, and reproducibility have made it the internationally recognized method for estimating the protein content in foods and it is the standard method against which all other methods are judged. It is also used to assay soils, wastewater, fertilizers, and other materials. It does not, however, give a measure of true protein content, as it measures non-protein nitrogen in addition to the nitrogen in proteins.