USGS Test Method I-2522-90


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Source:
USGS

Method Name:
Ammonia in Water by Colorimetry. Official Name: Nitrogen, Ammonia, Colorimetry, Salicylate-Hypochlorite, Automated-Segmented Flow

Description:
Ammonia reacts with salicylate and hypochlorite ions in the presence of ferricyanide ions to form the salicylic acid analog of indophenol blue (Reardon and others, 1966; Patton and Crouch, 1977; Harfmann and Crouch, 1989). The resulting color is directly proportional to the concentration of ammonia present.

Scope:
This method is used to analyze samples of surface, domestic, and industrial water, and brines containing from 0.01 to 1.5 mg/L of ammonia-nitrogen. Concentrations greater than 1.50 mg/L must be diluted. This modified method was implemented in the National Water Quality Laboratory in March 1988.

Citation:
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

Interferences:
Sulfide interferes. Bromide and nitrite can interfere. Calcium and magnesium in highly alkaline waters (pH greater than 13.6) can exceed the ability of the tartrate to complex both ions.The samples are easily contaminated by ammonia in the laboratory atmosphere; therefore, sample handling and analysis need to be performed where there is no possibility of ammonia contamination.

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

Media:
WATER

Subcategory:
Inorganic

Concentration:
0.01 - 1.5 (undiluted)

Precision:
Single operator precision for ammonia-nitrogen, as determined for natural-water samples, expressed as follows: 180, 193, 147, 252, 240, 209 and 240 determinations were performed with mean recoveries of 1.23, 0.17, 0.28, 0.71, 0.54, 0.06 and 0.12 mg/L with corresponding standard deviations of 0.011, 0.001, 0.004, 0.005, 0.006, 0.001, and 0.002, and 0.89, 0.59, 1.4, 0.70, 1.1, 1.7 and 1.7 %-RSD, respectively.

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

Revision Number:
1993

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