EPA-NERL: 360.2: Dissolved Oxygen Using a Modified Winkler Method
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Official Method Name
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Oxygen, Dissolved (Modified Winkler, Full-Bottle Technique) |
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Current Revision
| Issued 1971 |
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Media
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WATER |
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Instrumentation
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Titration |
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Method Subcategory
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Inorganic |
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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 treated with manganous sulfate, potassium hydroxide and potassium iodide, and finally sulfuric acid. The initial precipitate of manganous hydroxide combines with the dissolved oxygen in the sample to form a brown precipitate, manganic hydroxide. Upon acidification, the manganic hydroxide forms manganic sulfate which acts as an oxidizing agent to release free iodine from potassium iodide. The iodine, which is stoichiometrically equivalent to the dissolve oxygen in the sample is then titrated with sodium thiosulfate of phenylarsine oxide. |
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Scope and Application
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This method determines dissolved oxygen in most wastewaters and streams that contain nitrate nitrogen and not more than 1 mg/L of ferrous iron. |
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Applicable Concentration Range
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Not Available. |
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Interferences
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Chemical Agents: Oxidizing and reducing agents, nitrate ion, ferrous iron, and organic matter could effect test results. Modifications to the original Winkler procedure have overcome many interferences. In addition, the dissolved oxygen probe (EPA Method 360.1) is an alternative procedure which is subject to less interferences. |
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Quality Control Requirements
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None. |
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Sample Handling
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Collect samples in BOD bottles according to method recommendations, and record the temperature. If samples have applicable iron demand or ferrous iron concentration, analyze as soon as possible. If not, samples may be preserved (as described in the method) and analysis may occur between 4 and 8 hours after collection. |
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Maximum Holding Time
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8 hours (preserved) (MCAWW, Table 1). |
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Relative Cost
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Less than $50 |
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Sample Preparation Methods
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None. |
