The Reference Protein Determination Methods Kjeldahl and Dumas in Comparison - Which method is the better choice for the analytical scope in my lab?

Markus Kranz, C. Gerhardt GmbH & Co. KG, 53639 Königswinter, Germany (

For the determination of nitrogen and protein in food, there are different established methods. In the methods discussed here the nitrogen content of a sample is analysed and then, the protein content is calculated using a protein factor which is specific for the sample type: As well as the classic Kjeldahl method, nowadays the faster Dumas method has become more and more accepted. This can be seen from the fact

that the Dumas method is indicated as an additional reference method in various international standards. The author of this poster compares both methods, identifies decision criteria for and against these methods and illustrates the analytical performance by means of ring test results for different sample matrices.

Short Biography of Presenting Author

Markus Kranz is Vice President at C. Gerhardt in Königswinter, Germany. Markus qualified as a chemical engineer and joined Gerhardt 25 years ago as a Sales Engineer based in the South of Germany. His strong performance for Gerhardt in the field and knowledge of reference analysis for Nitrogen, protein, fat and fibre testing brought him success in the company and he was promoted to sales director. His analytical experience was then expanded within the company in support of product development and the company laboratory.

Now as Vice President, with 25 years of experience, he has a deep insight into the analytical market for the analysis of Nitrogen, protein, fat and fibre as well as extensive knowledge of the applications and engineering behind Gerhardt’s state of the art product development. Markus maintains his role as Sales Director and is responsible for a large network of distributors and product specialists who are taking care of Gerhardt’s customers throughout the world.

Markus is also the head of the application laboratory which besides testing Gerhardt’s new analytical equipment during and after development, participates regularly in several internationally recognised ring test schemes and interlaboratory tests for a wide range of samples. The laboratory at Gerhardt provides rapid, practical answers to application queries where customers are looking to optimise their analytical performance and results.

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