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522

Total Nitrogen and Carbon-Combustion Method

Summary

This analytical method quantitatively determines the total amount of nitrogen and carbon in botanical material using sample combustion coupled with either thermal conductivity/IR detection (LECO FP-528 and TruSpec CN Analyzers) or gas chromatography/thermal conductivity detection (Thermo-Finnigan Flash EA 1112).  The TruSpec CN Analyzer is the preferred instrument, but in the event of very limited sample material the Thermo-Finnigan Flash EA 1112 is used.  The instruments give equivalent test results.  The method is based on the oxidation of the sample by “flash combustion” which converts all organic and inorganic substances into combustion gases (N2, NOx, CO2, and H2O). The method has a detection limit of approximately 0.02% for nitrogen and 0.1% for carbon.

Best results are obtained when the samples appear powder-like. 

Sample amount requested:  3 g (for either or both)

Questions concerning limited sample size can be answered by the UC Davis Analytical Laboratory.

AOAC Official Method 972.43, Microchemical Determination of Carbon, Hydrogen, and Nitrogen, Automated Method, in Official Methods of Analysis of AOAC International, 18th edition, Revision 1, 2006. Chapter 12, pp. 5-6, AOAC International, Gaithersburg, MD.

AOAC Official Method 990.03. Protein (Crude) in Animal Feed, Combustion Method, in Official Methods of Analysis of AOAC International, 18th Edition (2005).  Revision 1, 2006, Chapter 4, pp. 30-31.  AOAC International, Arlington, VA.