The
Dumas method, also known as combustion method, is a primary method for the determination of Nitrogen and Protein ensuring fast results, ease-of-use and safety.
Unlike the commonly used Kjeldahl method, Dumas method, also known as elemental analysis or combustion method, detects the total nitrogen content, not only that which is contained within proteins.
The Dumas method for nitrogen determination, developed in 1831, is older than the Kjeldahl, 1883, but more convenient in many aspects such as speed, safety, cleanliness, productivity and cost per analysis.
How does an elemental analyzer work? Steps of the Dumas method Combustion
Once the sample is weighed and purged of any atmospheric gases, it is heated in a high-temperature furnace and rapidly combusted in the presence of pure oxygen at about 1,000 ºC. This leads to the release of substances such as carbon dioxide, water, nitrogen dioxide and, above all, nitrogen as several oxides (NyOx).
Sample + O2 → CO2 + H20 + NxOy + O2 + other oxides
Reduction and Separation
The combustion products are collected and allowed to equilibrate. The gas mixture is passed over hot copper to remove any oxygen and convert nitrogen oxides into molecular nitrogen. The sample is passed through traps that remove water and carbon dioxide.
CO2 + H20 + NxOy + O2 + Cu → CO2 + H20 + N2 → N2
Detection
The measured signal from the thermal conductivity detector for the sample can then be converted into total nitrogen content.
EDTA, aspartic acid, acetanilide, urea, atropine and other reagents can be used to create calibration curves in the DUMASoft™ software in order to translate in mgN the signal received from the TCD.