USGS-NWQL: I-6522-90: Ammonia in Sediment by Colorimetry

Summary
Analytes
Revision
Data and Sites

Official Method Name

Nitrogen, Ammonia, Colorimetry, Salicylate-Hypochlorite, Automated-Segmented Flow

Current Revision

1993

Media

SOILS/SEDIMENT

Instrumentation

Spectroscopy (Colorimetry; Photometry)

Method Subcategory

Inorganic

Method Source

USGS-NWQL

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

Brief Method Summary

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 and Application

This method is used to determine concentrations of ammonia-nitrogen in samples of bottom material containing at least 0.2 mg/kg NH₃-N. Prepared sample solutions containing more than 1.5 mg/L NH₃-N need to be diluted. Sodium ion is a good replacement for ammonium ion in the slow-exchange positions of soil minerals (Jackson, 1958). Bottom material is treated with an acidified sodium chloride solution, and the resulting mixture is allowed to settle and then decanted to obtain a clear supernatant solution for analysis.

Applicable Concentration Range

0.2-60

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.

Quality Control 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.

Sample Handling

Description: 500 mL polypropylene bottle, wide-mouth. Chill or maintain at 4^oC, ship immediately. Must arrive at 4^oC +/- 2^oC.

Maximum Holding Time

30 days from sampling

Relative Cost

Less than $50

Sample Preparation Methods

This method has 1 analyte associated with it.

Analyte	Detection Level	Bias	Precision	Pct False Positive	Pct False Negative	Spiking Level
Ammonia(7664-41-7) Ammonia Anhydrous ammonia Nitrogen, ammonia	0.200 mg/kg	N/A	N/A

Precision Descriptor Notes:	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 Level Note:	Method detection limits (MDLs) were determined for this method using the procedures of the U.S. Environmental Protection Agency (1997).

Precision Descriptor Notes:

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 Level Note:

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

Revision	PDF/Link
1993

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USGS-NWQL: I-6522-90: Ammonia in Sediment by Colorimetry

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