Dumas method

Dumas method

The Dumas method in analytical chemistry is a method for the quantitative determination of nitrogen in chemical substances based on a method first described by Jean-Baptiste Dumas over a century and a half ago.[1]

An automated instrumental technique has been developed which is capable of rapidly measuring the crude protein concentration of food samples and is beginning to compete with the Kjeldahl method as the standard method of analysis for protein content for some foodstuffs.

The method consists of combusting a sample of known mass in a high temperature (about 900°C) chamber in the presence of oxygen. This leads to the release of carbon dioxide, water and nitrogen. The gases are then passed over special columns that absorb the carbon dioxide and water. A column containing a thermal conductivity detector at the end is then used to separate the nitrogen from any residual carbon dioxide and water and the remaining nitrogen content is measured. The instrument must first be calibrated by analyzing a material that is pure and has a known nitrogen concentration. The measured signal from the thermal conductivity detector for the unknown sample can then be converted into a nitrogen content. As with the Kjeldahl method, conversion of the concentration of nitrogen in a sample to the crude protein content is performed using conversion factors which depend on the particular amino acid sequence of the measured protein.

The Dumas method has the advantages of being easy to use and automated. It is also considerably faster than the Kjeldahl method, taking a few minutes per measurement, as compared to the hour or more for Kjeldahl. It also does not make use of toxic chemicals or catalysts. One major disadvantage is its high initial cost. Also, as with Kjeldahl, it does not give a measure of true protein, as it registers nonprotein nitrogen, and different correction factors are needed for different proteins because they have different amino acid sequences. Finally, the small sample size raises the risk of obtaining an unrepresentative sample.

See also

References

  1. ^ Dr. D. Julian McClements. "Analysis of Proteins". University of Massachusetts. http://www-unix.oit.umass.edu/~mcclemen/581Proteins.html. Retrieved 2007-04-27. 

Wikimedia Foundation. 2010.

Игры ⚽ Нужно сделать НИР?

Look at other dictionaries:

  • Dumas method of molecular weight determination — The Dumas method of molecular weight determination was historically a procedure used to determine the molecular weight of an unknown substance. The Dumas method is appropriate to determine the molecular weights of volatile organic substances that …   Wikipedia

  • Dumas — is a Southern French topographic surname, with fused preposition and definite article du, for someone who lived in an isolated dwelling in the country rather than in a village, from Occitan mas farmstead (Late Latin mansum, mansus).[1] Contents 1 …   Wikipedia

  • Dumas, Jean-Baptiste-André — ▪ French chemist born July 14, 1800, Alais [now Alès], France died April 10, 1884, Cannes  French chemist who pioneered in organic chemistry (chemistry), particularly organic analysis.       Dumas s father was the town clerk, and Dumas attended… …   Universalium

  • Dumas , Jean Baptiste André — (1800–1884) French chemist Dumas was educated in classics at the college in his native city of Alais and intended to serve in the navy. However, after Napoleon s final defeat he changed his mind and became apprenticed to an apothecary. In 1816 he …   Scientists

  • Kjeldahl method — The Kjeldahl method in analytical chemistry is a method for the quantitative determination of nitrogen in chemical substances developed by Johan Kjeldahl during the 1800s. [Julius B. Cohen Practical Organic Chemistry 1910… …   Wikipedia

  • Jean-Baptiste Dumas — Born 14 July 1800 …   Wikipedia

  • Protein (nutrient) — This article is about protein as a nutrient. For protein as a class of molecule, see protein. For other uses, see bodybuilding supplement. Amino acids are the building blocks of protein. Proteins are polymer chains made of amino acids linked… …   Wikipedia

  • Protein adulteration in the People's Republic of China — refers to the adulteration and contamination of several food and feed ingredients with inexpensive melamine and other compounds such as cyanuric acid, ammeline and ammelide. These adulterants can be used to inflate the apparent protein content of …   Wikipedia

  • Chinese protein export contamination — was first identified after the wide recall of many brands of cat and dog food starting in March 2007 (the 2007 pet food recalls), and eventually involved the human food supply. The recalls in North America, Europe and South Africa came in… …   Wikipedia

  • Cervical cap — This article is about the contraceptive device. For devices used to help achieve pregnancy, see conception device. Cervical cap Oves brand cervical cap (discontinued) Background Birth control type …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”