ASTM: D6581: Oxyhalides in Water
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Official Method Name
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Standard Test Method for Bromate, Bromide, Chlorate, and Chlorite in Drinking Water by Chemically Suppressed Ion Chromatography |
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Current Revision
| Current edition approved July 10, 2000. Published October 2000. |
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Media
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WATER |
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Instrumentation
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Ion Chromatography |
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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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Oxyhalides (chlorite, bromate, and chlorate) and bromide in raw water, finished drinking water and bottled water are determined by ion chromatography. A sample (200 uL) is injected into an ion chromatograph and the pumped eluent (sodium carbonate) sweeps the sample through the analytical column set. Here, anions are separated from the sample matrix according to their retention characteristics, relative to the anions in the eluent. The separated anions in the eluent stream then pass through a suppressor device, where all cations are exchanged for hydronium ions. This converts the eluent to carbonic acid, thus reducing the background conductivity. This process also converts the sample anions to their acid form, thus enhancing their conductivity. The eluent stream then passes through a conductivity cell, where they are detected. A chromatographic integrator or appropriate computer-based data system is typically used for data presentation. The anions are identified based on their retention times compared to known standards. Quantification is accomplished by measuring anion peak areas and comparing them to the areas generated from known standards. |
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Scope and Application
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This test method covers the determination of the oxyhalides - chlorite, bromate, and chlorate, and bromide, in raw water, finished drinking water and bottled (non-carbonated) water by chemically suppressed ion chromatography. |
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Applicable Concentration Range
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20-500 except bromide at 20-200 and bromate at 5-30 ug/L |
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Interferences
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Positive errors can be caused by progressive oxidation of residual hypochlorite and/or hypobromite in the sample to the corresponding chlorate and bromate. Furthermore, chlorite can also be oxidized to chlorate, causing negative errors for chlorite and positive errors for chlorate. These interferences are eliminated by the sample preservation steps outlined in Section 8.5. Chloride present at > 200 mg/L and carbonate present at > 300 mg/L can interfere with bromate determination. These interferences can be minimized, or eliminated, by the sample pretreatment steps outlined in Section 8.6. Fluoride and low molecular weight monocarboxylic acids, present at mg/L concentrations, may interfere with the quantitation of chlorite and bromate. |
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Quality Control Requirements
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Minimum quality control requirements are initial demonstration of proficiency, plus calibration verification, analysis of method blanks, quality control samples, and recovery spikes and, duplicate samples. For a general discussion of quality control and good laboratory practices, see Guide D 3856. |
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Sample Handling
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Collect the sample in accordance with Practice D 3370, as applicable. Immediately upon taking the sample, sparge it with an inert gas (e.g., nitrogen, argon or helium) for 5 minutes to remove active gases such as chlorine dioxide or ozone. Add 1.00 mL of EDA Preservation Solution (8.5) per 1.000 litre of sample to prevent conversion of residual hypochlorite or hypobromite to chlorate or bromate. This also prevents metal catalyzed conversion of chlorite to chlorate. The oxyhalides in samples preserved in this manner are stable for at least 14 days when stored in amber bottles at 4oC |
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Maximum Holding Time
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14 days |
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Relative Cost
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Unknown |
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Sample Preparation Methods
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