Determination of crude protein in grain and grain products for food and feed by the Dumas Combustion Principle

Methods Type: 
Generic Methods
Key data
Crude Protein (Dumas Combustion Principle)
Grain and Grain Products for Food and Feed
Year of Approval: 

The measurement of the total nitrogen content in grain and grain products and, by calculation, protein content.

  • The sample is combusted in an oxygen-rich environment, at about 1000° C, to give oxides of nitrogen which are catalytically reduced to nitrogen. Other products resulting from the combustion phase are removed by selective absorption.
  • Nitrogen gas is measured with a thermal conductivity detector.
  • Total nitrogen is calculated from the detector response. The detector is calibrated with a known nitrogen standard.
  • Automatic combustion analysers rely on a carrier gas, such as helium or carbon dioxide.


Crude protein is a conventional expression of the total content of nitrogen compounds of the analysed product, calculated by multiplying the corresponding nitrogen content by a conversion factor.