Determination of nitrogen according to Dumas

The Dumas nitrogen determination is a measurement method named after the French chemist Jean-Baptiste Dumas (1800–1884) for the quantitative determination of the nitrogen content of flammable, mostly organic samples. It belongs to analytical chemistry and is part of many elemental analyzes .

An important application of the various methods for determining nitrogen is the estimation of the protein content of food or feed ; the conversion from nitrogen to protein content is carried out using a suitable factor. The Dumas nitrogen determination is often used for protein determination, for example in cereals and cereal products. Compared to the alternative Kjeldahl method , the Dumas method has the advantage that no hazardous substances have to be used. When using an automatic analyzer, an analysis takes three to four minutes.

Procedure for nitrogen determination according to Dumas

Manual procedure

The weighed sample substance is mixed with copper (II) oxide CuO and heated to red heat. The combustion gases are passed over hot copper in a stream of CO _{2 in} order to reduce any nitrogen oxides. Carbon dioxide CO ₂ is absorbed in potassium hydroxide and the remaining nitrogen is determined volumetrically. In the 19th century, the CO ₂ carrier gas flow was generated with the help of a Kipp apparatus .

Modern variants

In the modern variant, the quantification is no longer carried out volumetrically. Instead, the amount of nitrogen in the carrier gas flow - which can also consist of helium - is determined with the help of a thermal conductivity detector and a suitable calibration.

Historical

Jean-Baptiste Dumas published the procedure in 1833; he first applied it to the analysis of indigo . Using the empirical formula C ₁₆ H ₁₀ N ₂ O ₂ known today , a nitrogen content of w (N) = 10.68% is calculated; At that time Dumas gave values of 10.30% and 10.80%.

Fritz Pregl , who received the Nobel Prize for Chemistry in 1923 “for the microanalysis of organic substances he developed” , had also further developed the Dumas method for his microanalyses , so that it has since been able to be carried out with significantly smaller amounts of substance. In his lecture on the Nobel Prize, he described difficulties that he had to overcome. For example, he gained a CO ₂ stream from marble and hydrochloric acid. It turned out that the solubility of air or nitrogen in the acid was unexpectedly high and thus initially falsified the results.

In the late 1950s and early 1960s, various machines were invented to perform the analysis. This enabled six analyzes to be carried out per hour, with 1–10 mg of sample substance each being required.

Individual evidence

↑ ^a ^b Introductory article to DIN EN ISO 16634-1: 2009-07 (Food products - Determination of the total nitrogen content with the Dumas incineration method and calculation of the crude protein content - Part 1: Oilseed meal and animal feed)

↑ ^a ^b Determination of the protein content using the DUMAS combustion method, information sheet of the Arbeitsgemeinschaft Getreideforschung eV, Detmold, December 1999

↑ Nitrogen determination according to Dumas , page 6 of the text accompanying the lecture Experimental Chemistry, Prof. H. Mayr at the University of Munich

^ ^A ^b Jean-Baptiste Dumas: Recherches de Chimie organique . read on August 5, 1833. In: Joseph Louis Gay-Lussac, François Arago (ed.): Annales de chimie et de physique . tape 53 . Crochard, Paris 1833, p. 164–181 ( online at Gallica [accessed on February 23, 2016] nitrogen determination from page 171).

^ Fritz Pregl: Quantitative Micro-Analysis of Organic Substances. Nobel Lecture. In: Nobel Prizes and Laureates. Nobelprize.org, December 11, 1923, accessed February 25, 2016 .

↑ Irmgard KH Otter: Swift Dumas Nitrogen Estimation . In: Nature . tape 182 , no. 4636 , September 6, 1958, p. 656-657 , doi : 10.1038 / 182656a0 (Loughborough Glass Company / Fisons Pest Control).

^ ^A ^b Grant M. Gustin: A simple, rapid automatic micro-Dumas apparatus for nitrogen determination . In: Microchemical Journal . tape 4 , no. 1 . Interscience, March 1960, ISSN 0026-265X , p. 43-54 , doi : 10.1016 / 0026-265X (60) 90066-7 (Celanese Corporation).

[DINENISO16634-1] Introductory article to DIN EN ISO 16634-1: 2009-07 (Food products - Determination of the total nitrogen content with the Dumas incineration method and calculation of the crude protein content - Part 1: Oilseed meal and animal feed)

[AGF-2] Determination of the protein content using the DUMAS combustion method, information sheet of the Arbeitsgemeinschaft Getreideforschung eV, Detmold, December 1999

[3] Nitrogen determination according to Dumas , page 6 of the text accompanying the lecture Experimental Chemistry, Prof. H. Mayr at the University of Munich

[Dumas-4] A ^b Jean-Baptiste Dumas: Recherches de Chimie organique . read on August 5, 1833. In: Joseph Louis Gay-Lussac, François Arago (ed.): Annales de chimie et de physique . tape 53 . Crochard, Paris 1833, p. 164–181 ( online at Gallica [accessed on February 23, 2016] nitrogen determination from page 171).

[5] Fritz Pregl: Quantitative Micro-Analysis of Organic Substances. Nobel Lecture. In: Nobel Prizes and Laureates. Nobelprize.org, December 11, 1923, accessed February 25, 2016 .

[6] Irmgard KH Otter: Swift Dumas Nitrogen Estimation . In: Nature . tape 182 , no. 4636 , September 6, 1958, p. 656-657 , doi : 10.1038 / 182656a0 (Loughborough Glass Company / Fisons Pest Control).

[Gustin-7] A ^b Grant M. Gustin: A simple, rapid automatic micro-Dumas apparatus for nitrogen determination . In: Microchemical Journal . tape 4 , no. 1 . Interscience, March 1960, ISSN 0026-265X , p. 43-54 , doi : 10.1016 / 0026-265X (60) 90066-7 (Celanese Corporation).