Nitrogen analyzer is an instrument for detecting nitrogen content in seeds, dairy products, beverages, feed, soil and other agricultural and sideline products. According to the principle of nitrogen determination, nitrogen analyzer is divided into Kjeldahl nitrogen analyzer and Dumas nitrogen analyzer. Now, let's take a look at the principles, advantages and disadvantages of these two nitrogen analyzers.
I. Kjeldahl nitrogen analyzer
The principle of Kjeldahl nitrogen analyzer is Kjeldahl method. Kjeldahl method is a method to determine the total nitrogen content in a compound or mixture, that is, in the presence of a catalyst, the sample is digested with concentrated sulfuric acid to convert all organic nitrogen into inorganic ammonium salt, and then the ammonium salt is converted into ammonia under alkaline conditions, which is distilled out with steam and absorbed by the excess boric acid solution, and then titrated with standard hydrochloric acid to calculate the amount of nitrogen in the sample. Since protein nitrogen content is relatively constant, protein content can be calculated from its nitrogen content, so this method is a classic protein quantitative method.
Kjeldahl method is a commonly used method for analyzing the nitrogen content of organic compounds or mixtures. It is one of the most accurate and simple methods for determining the total organic nitrogen in a sample. It is used as a legal standard inspection method at home and abroad. Kjeldahl method has a wide range of applications, accurate measurement results, and good reproducibility, but the operation is complicated and time-consuming with heavy workload. Kjeldahl nitrogen analyzer can be widely used 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.
II. Dumas Nitrogen Analyzer
The principle of Dumas nitrogen analyzer is Dumas combustion nitrogen analysis (Dumas method). Dumas combustion nitrogen analysis is to encapsulate a certain amount of sample in an aluminum boat, and then burn it in a high-temperature furnace. In the environment of catalyst and oxygen, the gases generated after the sample is burned are: CO2, H2O, NOx. When these gases pass through the reduction furnace, NOx is reduced to N2, while CO2 and H2O are separated, and finally, the nitrogen is measured by the thermal conductivity detector (TCD). The entire measurement process is completed within 3 minutes.
Now in some countries and regions around the world, especially developed countries in Europe and America, Dumas method has become a legal nitrogen/protein analysis method. In some areas of the United States, Canada and Germany, Dumas method is even regarded as the only standard for determining nitrogen.
However, Dumas method also has certain limitations. For example, the analysis of complex samples is more difficult, and the analysis of liquid samples is not effective. The sample needs to be uniform powder and finer. These limitations result from the certain limitations of analysis principle that cannot be avoided for the time being. In addition, the high price of Dumas nitrogen analyzer limits the promotion and application of this method.