Kjeldahlmódszer

The Kjeldahl method is a chemical procedure used to determine the nitrogen content in a sample. It was developed by the Danish chemist Johan Kjeldahl in 1883. The method is widely used in various fields, including agriculture, environmental science, and food analysis. The process involves several steps: digestion, distillation, and titration.

In the digestion step, the sample is treated with a mixture of sulfuric acid and potassium sulfate to convert organic nitrogen into ammonium sulfate. This step ensures that all nitrogen compounds are converted into a form that can be easily quantified.

Next, the sample is distilled. During this step, the ammonium sulfate is heated, causing it to decompose into ammonia and water vapor. The ammonia is then absorbed in a solution of boric acid, which stabilizes it as ammonium borate.

Finally, in the titration step, the ammonia is titrated with a standard acid solution, such as sulfuric acid. The amount of acid required to neutralize the ammonia is proportional to the amount of nitrogen in the original sample. This allows for the calculation of the nitrogen content in the sample.

The Kjeldahl method is known for its simplicity and reliability. However, it has limitations, such as the potential for losses of nitrogen during the digestion step and the need for careful handling of the reagents to avoid contamination. Despite these limitations, the Kjeldahl method remains a valuable tool in analytical chemistry.