Principle & Application Scope of Kjeldahl Nitrogen Analyzer
Kjeldahl nitrogen analyzer is an instrument that calculates the protein content by measuring the nitrogen content in the sample based on the principle of constant nitrogen content in protein. The method of protein content measurement and calculation is called Kjeldahl method, so it is called Kjeldahl nitrogen analyzer, also known as nitrogen analyzer, protein analyzer, and crude protein analyzer.
The organic compound is heated with sulfuric acid to convert the nitrogen therein into ammonium sulfate. In this step, potassium sulfate is often added to the mixture to increase the boiling point of the intermediate product. The end of the sample analysis process is easy to judge, because the mixture will become colorless and transparent at this moment (it is dark at the beginning).
A small amount of sodium hydroxide is added to the resulting solution and then distilled. This step converts the ammonium salt into ammonia. The total ammonia content (directly determined by the nitrogen content of the sample) will be determined by back titration: the end of the condenser tube will be immersed in the boric acid solution. Ammonia will react with acid, and excess acid will be titrated with sodium carbonate under the direction of methyl orange. The result of the titration is multiplied by a specific conversion factor to get the result.
II. Application scope
Kjeldahl nitrogen analyzer uses Kjeldahl method to detect the content of ammonia, protein nitrogen, phenol, volatile fatty acid, cyanide, sulfur dioxide, ethanol, etc. in grains, food, feed, water, soil, silt, sediment and chemicals. It has a very good price-performance ratio. Only the titration process requires manual operation, so Kjeldahl nitrogen analyzer is very suitable for routine testing of laboratories and inspection institutions, which is widely used in the analysis of nitrogen or protein content in food, crops, seeds, soil, fertilizers and other samples.