The Kjeldahl method, the laboratory technique for determining the amount of nitrogen in organic compounds, stems from research undertaken at the Carlsberg Laboratory in 1883.
Johan Kjeldahl (1849-1900), head of the Chemistry Department, developed the process to assist his studies into the protein content of various grains used for brewing – less protein meant more beer. He needed to measure nitrogen as this is one of the major elements found in protein, but existing techniques were unreliable or inaccurate.
Worldwide and widespread
At its most basic, his new method involved digesting the organic compound with sulphuric acid, distilling the ammonia produced and back titrating the solution with caustic soda.
The Kjeldahl method is still the standard method used worldwide today for calculating the protein content of substances ranging from foodstuffs to fertiliser and fossil fuels. While other methods may now be faster or more efficient, none can handle the same variety of sizes or conditions of samples.