What is difference between Dumas nitrogen analyzer and Kjeldahl nitrogen analyzer

What is difference between Dumas nitrogen analyzer and Kjeldahl nitrogen analyzer

1.Different work princple 

The Dumas method, also known as the combustion method, is a primary method of determination of Nitrogen and Protein ensuring fast results, ease of use, and safety.

Dumas nitrogen determination requires well-homogenized samples, heated in a high-temperature furnace where the combustion takes place rapidly at over 1000 °C in the presence of pure oxygen. This produces mostly water, carbon dioxide and nitrogen as several oxides (NyOx). This gas mixture passes through a reduction chamber containing copper heated to around 650 °C. This stage converts nitrogen oxides into elemental nitrogen and collects the oxygen in excess. Different traps remove the residual water and carbon dioxide. Total nitrogen content is measured by a thermal conductivity detector.

Kjeldahl nitrogen method is an analytical method for determining nitrogen content in certain organic and inorganic compounds. 

It including 3 operation steps : Digestion--Distillation---Titration. 

2.Validated by different international organizations:

Kjeldahl is officially recognized by AOAC, EPA, DIN, ISO, etc., 

whilst Dumas by AOAC, AACC, ISO, DIN, ASBC, AOCS, OIV, etc.

3.Different analysis time : 

The Dumas method has the advantage of being easy to use and automated. It is also considerably faster than the Kjeldahl method, taking 3~6 minutes per measurement,as compared to an hour or more for Kjeldahl. 

4.Measuring range difference

Dumas nitrogen analysis range : 0.1~500mgN,accuracy : ≤0.1mgN,Detect limit 0.01mgN

Kjeldahl nitrogen analysis range : 0.1~240mgN,accuracy ≤0.5%

5.Environment friendly difference

It also does not make use of toxic or harmful chemicals or catalysts. The Kjeldahl method uses concentrated sulfuric acid and a catalyst for digestion of samples. There will be produced lots of acid mist during sample digestion,it is not good for environment.

Dumas nitrogen analyzer	Kjeldahl nitrogen analyzer