Standard Methods: 4500-NH3 B: Ammonia: Preliminary Distillation Step
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Official Method Name
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4500-NH3 B. Preliminary Distillation Step |
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Current Revision
| Standard Methods 21st Edition (2005); Standard Methods Online |
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Media
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WATER |
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Instrumentation
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Preparatory Procedure |
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Method Subcategory
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Sampling/Preparation |
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Method Source
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Citation
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Brief Method Summary
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The sample is buffered at pH 9.5 with a borate buffer to decrease hydrolysis of cyanates and organic nitrogen compounds. It is distilled into a solution of boric acid when titration is to be used or into H2SO4 when the phenate method is used. Ammonia in the distillate also can be ~ determined by the ammonia-selective electrode method, using 0.04N H2SO4 to trap the ammonia. |
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Scope and Application
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The two major factors that influence selection of the method to determine ammonia are concentration and presence of interferences. In general, direct manual determination of low concentrations of ammonia is confined to drinking waters, clean surface or groundwater, and good-quality nitrified wastewater effluent. In other instances, and where interferences are present or greater precision is necessary, a preliminary distillation step is required. |
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Applicable Concentration Range
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Interferences
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Quality Control Requirements
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Sample Handling
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Most reliable results are obtained on fresh samples. If samples are to be analyzed within 24 h of collection, refrigerate unacidified at 4 degrees C. For preservation for up to 28 days, freeze at -20 degrees C unacidified, or preserve samples by acidifying to pH < 2 and storing at 4 degrees C. If acid preservation is used, neutralize samples with NaOH or KOH immediately before making the determination. |
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Maximum Holding Time
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28 days (regulatory) |
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Relative Cost
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Less than $50 |
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Sample Preparation Methods
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