Method 350.1

Ammonia nitrogen (Colorimetric, Automated Phenate)

This method is for the determination of ammonia in drinking, surface and saline waters, domestic and industrial wastes in the range of 0.01 to 2.0 mg/L ammonia as nitrogen.

The sample is buffered at a pH of 9.5 with a borate buffer to decrease hydrolysis of cyanates and organic nitrogen compounds and is distilled into a solution of boric acid and analyzed by colorimetry.

Calcium and magnesium ions can cause errors by precipitating during the analysis.  EDTA (ethylenediamine tetraacetate) or potassium tartrate solution can be used to reduce this interference.  Sample turbidity should be removed by filtration.  Color absorbing in the range of the indophenol blue complex can interfere with the analysis.

(EPA: Office of Water)


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Method Data

Hold Times, Preservatives, Preps, Collection, Analytical & Documentation
Holding Time:   28 days from sample collection to analysis.
Preservatives:   Preserve to pH <2 with concentrated H2SO4 and cool to 4°C.
Required Preps:   125mL plastic or glass bottle with a Teflon-lined lid
Collection Method:   Grab sampling
Analytical Methodology:   Colorimetry
Documentation:   350.1

Analyte List*

Analyte Formula CAS Number Detection Limit

* The analytes and detection limits listed for each method represent the typical detection limits and analytes reported for that particular method. Keep in mind that analyte lists may vary from laboratory to laboratory. Detection limits may also vary from lab to lab and are dependent upon the sample size, matrix, and any interferences that may be present in the sample.