USGS Test Method I-2540-90

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Method Name:
Nitrite in Water by Colorimetry. Official Name: Nitrogen, Nitrite, Colorimetry, Diazotization, Automated-Segmented Flow

Nitrite ion reacts with sulfanilamide under acidic conditions to form a diazo compound which then couples with N-1-naphthylethylenediamine dihydrochloride to form a red compound, the absorbance of which is measured colorimetrically (Shinn, 1941; Bendschneider and Robinson, 1952; Fox, 1979, 1985; Pai and others, 1990).

This method is used to analyze samples of surface, domestic, and industrial water and brines containing from 0.01 to 1.0 mg/L of nitrite-nitrogen. Concentrations greater than 1.0 mg/L must be diluted. This modified method was implemented in the National Water Quality Laboratory in March 1988.

M.J. Fishman, 1993, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory--Determination of inorganic and organic constituents in water and fluvial sediments: U.S. Geological Survey Open-File Report 93-125

Concentrations of potentially interfering substances generally are negligible. For specific details of inorganic and organic compounds that interfere with the reaction, see Norwitz and Keliher (1985, 1986) as well as more general information from the American Society for Testing and Materials (1991).

QC Requirements:
Quality-control samples area analyzed at a minimum of one in every ten samples. These QC samples include at least one of each of the following: blanks, quality control samples, third party check solutions, replicates, and spikes. Correlation coefficients for calibration curves must be at least 0.99. QC samples must fall within 1.5 standard deviations of the mean value. If all of the data-acceptance criteria in the SOPs are met, then the analytical data are acceptable.

Maximum Holding Time:
30 days from sampling



0.01 - 1.0 (undiluted)

Single operator precision for nitrite-nitrogen, as determined for natural-water samples is as follows: a series of 240, 209 and 240 determinations were made with mean recoveries of 0.05, 0.03 and 0.26 mg/L with 0.001, 0.001 and 0.001 mg/L standard deviations and 2.0, 3.3 and 0.38 %-RSD, respectively.

Method detection limits (MDLs) were determined for this method using the procedures of the U.S. Environmental Protection Agency (1997).

Revision Number:

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Analytical testing dots