525 TOTAL NITROGEN IN BOTANICAL MATERIALS - COMBUSTION METHOD (LECO FP528)
N
Total Nitrogen by Nitrogen Gas Analyzer utilizing induction furnace and thermal conductivity (LECO FP-528).
Summary: This method quantitatively determines the amount of nitrogen in all forms (ammonium, nitrate, protein and heterocyclic nitrogen) in botanical materials using an induction furnace and a thermal conductivity detector. Samples are ignited in an induction furnace at approximately 900°C, in helium and oxygen environment in a quartz combustion tube. An aliquot of the combustion gases is passed through a copper catalyst to remove oxygen and convert nitrous oxides to N2, scrubbed of moisture and carbon dioxide, and nitrogen content determined by thermal conductivity. The method has a detection limit of 0.01% nitrogen (dry basis) and is generally reproducible within 5%.
AOAC Official Method 990.03. Protein (Crude) in Animal Feed. 16th Edition (1997), AOAC International. Combustion Method. Arlington, VA.