Standard Methods: 4500-ClO2 E: Chlorine by Amperometry
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Official Method Name
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4500-ClO2 E. Amperometric Method II |
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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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Amperometer |
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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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Like Amperometric Method I (4500-ClO2 C), this procedure entails successive titrations of combinations of chlorine species. Subsequent calculations determine the concentration of each species. |
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Scope and Application
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The method is useful when a knowledge of the various chlorine fractions in a water sample is desired. It distinguishes various chlorine compounds of interest with good accuracy and precision, but requires specialized equipment and considerable analytical skill. |
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Applicable Concentration Range
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10 - 100 mg/L |
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Interferences
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At pH values above 4, significant iodate formation is possible if iodine is formed in the absence of iodide; this results in a negative bias in titrating the first and second samples. A positive bias results from oxidation of iodide to iodine by dissolved oxygen in strongly acidic solutions. The potential for interferences from manganese, copper, and nitrate are minimized by buffering the sample to pH > or = 4. |
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Quality Control Requirements
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See Section 4020 Quality Assurance/Quality Control. |
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Sample Handling
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Plastic or glass containers. Determine ClO2 promptly after collecting the sample. Do not expose sample to sunlight or strong artificial light and do not aerate to mix. Method can be performed on site, with prior calibration in the laboratory. Minimum ClO2 losses occur when the determination is completed immediately at the site of sample collection. |
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Maximum Holding Time
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0.25 hour |
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Relative Cost
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Greater than $400 |
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Sample Preparation Methods
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