While acid digestion according to Kjeldahl destroys the organic sample in a rather rustic way, combustion offers a more elegant and time-saving option. The sample is oxidised in a controlled manner and the resulting gaseous products are subjected to further analysis. The aim is the complete conversion of the sample into the main products carbon dioxide, water and nitrogen dioxide, without the by-products carbon monoxide CO and nitrogen monoxide NO resulting from incomplete combustion.
Modern combustion instruments such as the DUMATHERM® still use the principle of the Dumas method to determine nitrogen and protein content in solid and liquid samples. The entire analysis procedure is performed in 5 steps.
The sample enters the Dumas system via the sample changer (AS). In the combustion reactor (CF) an exothermic reaction occurs at 1030 °C between oxygen (O2) and tin capsule, which results in complete combustion of the sample. With the aid of oxidation catalysts it is made sure that the combustion gases are completely oxidized.