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Wikipedia

Combustion analysis

January 01, 1970

Combustion analysis is a method used in both organic chemistry and analytical chemistry to determine the elemental composition (more precisely empirical formula) of a pure organic compound by combusting the sample under conditions where the resulting combustion products can be quantitatively analyzed. Once the number of moles of each combustion product has been determined the empirical formula or a partial empirical formula of the original compound can be calculated.

Applications for combustion analysis involve only the elements of carbon (C), hydrogen (H), nitrogen (N), and sulfur (S) as combustion of materials containing them convert these elements to their oxidized form (CO2, H2O, NO or NO2, and SO2) under high temperature high oxygen conditions. Notable interests for these elements involve measuring total nitrogen in food or feed to determine protein percentage, measuring sulfur in petroleum products, or measuring total organic carbon (TOC) in water.

History edit

The method was invented by Joseph Louis Gay-Lussac. Justus von Liebig studied the method while working with Gay-Lussac between 1822 and 1824 and improved the method in the following years to a level that it could be used as standard procedure for organic analysis.[1]

Combustion train edit

A combustion train is an analytical tool for the determination of elemental composition of a chemical compound. With knowledge of elemental composition a chemical formula can be derived. The combustion train allows the determination of carbon and hydrogen in a succession of steps:

Analytical determination of the amounts of water and carbon dioxide produced from a known amount of sample gives the empirical formula. For every hydrogen atom in the compound 1/2 equivalent of water is produced, and for every carbon atom in the compound 1 equivalent of carbon dioxide is produced.

Nowadays, modern instruments are sufficiently automated to be able to do these analyses routinely. Samples required are also extremely small — 0.5 mg of sample can be sufficient to give satisfactory CHN analysis.

CHN analyzer edit

A CHN analyzer (also known as a carbon hydrogen and nitrogen analyzer) is a scientific instrument which is used to measure carbon, hydrogen and nitrogen elemental concentrations in a given sample with accuracy and precision.[2] Sample sizes are most often just a few milligrams, but may differ depending on system. For some sample matrices larger mass is preferred due to sample heterogeneity. These analysers are capable of handling a wide variety of sample types, including solids, liquids, volatile and viscous samples, in the fields of pharmaceuticals, polymers, chemicals, environment, food and energy.[3]

This instrument calculates the percentages of elemental concentrations based on the Dumas method, using flash combustion of the sample to cause an instantaneous oxidization into simple compounds which are then detected with thermal conductivity detection or infrared spectroscopy.[4] Separation of interference is done by chemical reagents.

Modern methods edit

The water vapor, carbon dioxide and other products can be separated via gas chromatography and analysed via a thermal conductivity detector.[5]

See also edit

References edit

  1. ^ Frederic L. Holmes (1963). "Elementary Analysis and the Origins of Physiological Chemistry". Isis. 54 (1): 50–81. doi:10.1086/349664. JSTOR 228728. S2CID 94123953.
  2. ^ "CHN Analysis". www.intertek.com. Retrieved 2019-04-22.
  3. ^ "CHNS Elemental Analysers" (PDF). April 2008. Retrieved 2019-04-22.
  4. ^ . www.rsic.iitb.ac.in. Archived from the original on 2009-07-09. Retrieved 2019-04-22.
  5. ^ Pavia, Donald (2008). Introduction to spectroscopy. Brooks Cole. p. 2. ISBN 978-0495114789.

External links edit

  • ECO Core Analytical Services: Elemental Analysis
  • Geostandards and Geological Research
  • Luvak Laboratories

January 01, 1970
combustion, analysis, method, used, both, organic, chemistry, analytical, chemistry, determine, elemental, composition, more, precisely, empirical, formula, pure, organic, compound, combusting, sample, under, conditions, where, resulting, combustion, products,. Combustion analysis is a method used in both organic chemistry and analytical chemistry to determine the elemental composition more precisely empirical formula of a pure organic compound by combusting the sample under conditions where the resulting combustion products can be quantitatively analyzed Once the number of moles of each combustion product has been determined the empirical formula or a partial empirical formula of the original compound can be calculated Applications for combustion analysis involve only the elements of carbon C hydrogen H nitrogen N and sulfur S as combustion of materials containing them convert these elements to their oxidized form CO2 H2O NO or NO2 and SO2 under high temperature high oxygen conditions Notable interests for these elements involve measuring total nitrogen in food or feed to determine protein percentage measuring sulfur in petroleum products or measuring total organic carbon TOC in water Contents 1 History 2 Combustion train 3 CHN analyzer 4 Modern methods 5 See also 6 References 7 External linksHistory editThe method was invented by Joseph Louis Gay Lussac Justus von Liebig studied the method while working with Gay Lussac between 1822 and 1824 and improved the method in the following years to a level that it could be used as standard procedure for organic analysis 1 Combustion train editA combustion train is an analytical tool for the determination of elemental composition of a chemical compound With knowledge of elemental composition a chemical formula can be derived The combustion train allows the determination of carbon and hydrogen in a succession of steps combustion of the sample at high temperatures with Copper II oxide as the oxidizing agent collection of the resulting gas in a hygroscopic agent magnesium perchlorate or calcium chloride to trap generated water collection of the remainder gas in a strong base for instance potassium hydroxide to trap generated carbon dioxide Analytical determination of the amounts of water and carbon dioxide produced from a known amount of sample gives the empirical formula For every hydrogen atom in the compound 1 2 equivalent of water is produced and for every carbon atom in the compound 1 equivalent of carbon dioxide is produced Nowadays modern instruments are sufficiently automated to be able to do these analyses routinely Samples required are also extremely small 0 5 mg of sample can be sufficient to give satisfactory CHN analysis CHN analyzer editA CHN analyzer also known as a carbon hydrogen and nitrogen analyzer is a scientific instrument which is used to measure carbon hydrogen and nitrogen elemental concentrations in a given sample with accuracy and precision 2 Sample sizes are most often just a few milligrams but may differ depending on system For some sample matrices larger mass is preferred due to sample heterogeneity These analysers are capable of handling a wide variety of sample types including solids liquids volatile and viscous samples in the fields of pharmaceuticals polymers chemicals environment food and energy 3 This instrument calculates the percentages of elemental concentrations based on the Dumas method using flash combustion of the sample to cause an instantaneous oxidization into simple compounds which are then detected with thermal conductivity detection or infrared spectroscopy 4 Separation of interference is done by chemical reagents Modern methods editThe water vapor carbon dioxide and other products can be separated via gas chromatography and analysed via a thermal conductivity detector 5 See also editElementar a large manufacturer of combustion analyzers LECO Corporation a large manufacturer of combustion analyzers Kjeldahl method an alternative analysis of CHN contentReferences edit Frederic L Holmes 1963 Elementary Analysis and the Origins of Physiological Chemistry Isis 54 1 50 81 doi 10 1086 349664 JSTOR 228728 S2CID 94123953 CHN Analysis www intertek com Retrieved 2019 04 22 CHNS Elemental Analysers PDF April 2008 Retrieved 2019 04 22 CHNS O Analyzer www rsic iitb ac in Archived from the original on 2009 07 09 Retrieved 2019 04 22 Pavia Donald 2008 Introduction to spectroscopy Brooks Cole p 2 ISBN 978 0495114789 External links editECO Core Analytical Services Elemental Analysis Geostandards and Geological Research Luvak Laboratories Retrieved from https en wikipedia org w index php title Combustion analysis amp oldid 1131283160, wikipedia, wiki, book, books, library,

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