NEMI Method Summary

Method Summary Information

Method Number: 351.2 Media: WATER
Revision: Issued 1978
Method Source: U.S. EPA National Exposure Research Laboratory (NERL) [formerly EMSL]
Analytes in this method
Subcategory: INORGANIC
Official Name: Nitrogen, Kjeldahl Total (Colorimetric, Semi-Automated Block Digestor, AAII)
Descriptive Name TKN by Semi-Automated Block Digestion and Colorimetry
Source Info: U.S.EPA National Exposure Research Laboratory (NERL)
Microbiological and Chemical Exposure Assessment Research Division (MCEARD)
[formerly the Environmental Monitoring Systems Laboratory (EMSL), Cincinnati, OH]
26 West Martin Luther King Drive
Cincinnati, Ohio 45268-0001
Fax: 513-569-7757
email: DWmethods.help@epa.gov
Citation: Methods for the Chemical Analysis of Water and Wastes (MCAWW) (EPA/600/4-79/020)
74187 Byte file
Brief Method
Summary:
 This is a semi-automated method. A sample is heated in the presence of sulfuric acid, potassium sulfate, and mercuric sulfate for two and one half hours. The digestion converts nitrogen components of biological origin (e.g., amino acids, proteins, and peptides) to ammonia, but may not convert some compounds in industrial wastes (e.g., certain amines and refractory tertiary amines, nitro compounds, hydrazones, oximes, semicarbazones). The resulting residue is cooled, diluted to 25 mL and placed on the AutoAnalyzer for ammonia determination by colorimetry. This digested sampled also may be used for phosphorus determination.
Scope And
Application:
 This method determines total Kjeldahl nitrogen in drinking water and surface waters; domestic and industrial wastes.
Applicable
Conc Range:
 0.1 to 20 mg/L TKN.
Interferences: None given.
QC Requirements: None
Sample Handling: Samples may be preserved by adding 2 mL of concentrated sulfuric acid per liter of sample and storing at 4oC. However, even with preservation, organic nitrogen can convert to ammonia. Therefore, analyze samples as soon as possible.
Max Holding Time:
 28 days (MCAWW, Table 1).
 
Relative Cost: Less than $50
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