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

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Methods Type: Generic Methods
Key data
Number: 167
Analyte: Crude Protein (Dumas Combustion Principle)
Matrix: Grain and Grain Products for Food and Feed
Year of Approval: 2000
Scope: The measurement of the total nitrogen content in grain and grain products and, by calculation, protein content.
Principle: 
  • 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.

Definition

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.

 

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