NEMI Method Summary

Method Summary Information

Method Number: I-2545 Media: WATER
Revision: 1973
Method Source: U.S. Geological Survey (USGS)
Subcategory: INORGANIC Analytes in this method
Official Name: Nitrogen, nitrite plus nitrate, colorimetry, cadmium reduction-diazotization, automated-segmented flow
Descriptive Name Nitrogen, nitrite plus nitrate, dissolved, colorimetric, ASF
Source Info: USGS Branch of Information Services
Box 25286, MS 417
Federal Center
Denver, CO 80225-0286
Phone: 303-202-4700
Citation: U.S. Geological Survey Open-File Report 93-125
244255 Byte file
Brief Method
Summary:
 An acidified sodium chloride extraction procedure is used to extract nitrate and nitrite from samples of bottom material for this determination (Jackson, 1958).
Nitrate is reduced to nitrite by cadmium metal. Imidazole is used to buffer the analytical stream. The sample stream then is treated with sulfanilamide to yield a diazo compound, which couples with N-1naphthylethylenediamine dihydrochloride to form an azo dye, the absorbance of which is measured colorimetrically. The result is the sum of the nitrite originally present plus that formed by the reduction of the nitrate (Morris and Riley, 1963; Brewer and Riley, 1965; Wood and others, 1967; Strickland and Parsons, 1972; Nydahl, 1976; Sherwood and Johnson, 1981; Patton, 1982; U.S. Environmental Protection Agency, 1983).
Scope And
Application:
 This method is used to analyze samples of surface, domestic, and industrial water and brines containing from 0.05 to 5.0 mg/L of nitrite- plus nitrate-nitrogen. Samples containing greater concentrations must be diluted. Originally started in 1973, this modified method was implemented in the National Water Quality Laboratory in March 1988.
Applicable
Conc Range:
 0.05 to 5.0 mg/L
Interferences: Concentrations of potentially interfering substances generally are negligible in unpolluted surface and ground water. For specific details of inorganic and organic compounds that interfere, see Norwitz and Keliher (1985, 1986) as well as more general information from the American Society for Testing and Materials (1991).
Sulfides, often present in anoxic water, rapidly deactivate cadmium reactors by forming an insoluble layer of cadmium sulfide on the active metal surface (Strickland and Parsons, 1972).
The buffer capacity of the imidazole solution and the approximate 10:1 volume ratio of buffer to sample eliminate the possibility of erroneous results for moderately acidic (pH > 1) samples.
Mercury (II) does not interfere. It rapidly forms an amalgam on the inlet end of the cadmium reactor without detriment to the reduction reaction.
QC Requirements: Calibrate instrument using calibration standards (CAL); quality control samples (QCS); and laboratory blanks (LB) analyzed at a minimum of 1 for every 10 samples.
Sample Handling: Container Description: 125 mL brown polyethylene bottle.
Treatment and Handling: Filter through 0.45 micron filter; use filtered sample to rinse container; preservation with mercuric chloride; chilled to 4 degrees C and ship immediately.
Max Holding Time:
 30 days
 
Relative Cost: Less than $50
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