EPA-OGWDW/TSC: 317.0rev2.0: Inorganic Oxyhalide DBPs in Drinking Water By Ion Chromatography With Conductivity Detection and Trace Bromate Using Post Column Reagent Colorimetry
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Official Method Name
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Determination of Inorganic Oxyhalide Disinfection By-products in Drinking Water Using Ion Chromatography With the Addition of a Postcolumn Reagent for Trace Bromate Analysis |
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Current Revision
| Revision 2.0, July 2001 |
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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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About a quarter of a milliliter of sample is introduced directly into an ion chromatograph equipped with a guard column and a suppressor device. The target anions are separated and measured using an analytical column and a conductivity detector. In addition trace bromate analysis is achieved using a postcolumn reagent delivery system, a heated postcolumn reaction coil, and a ultraviolet/visible (UV/VIS) absorbance detector. Bromide should not be determined in finished water because its concentration can differ significantly between preserved and unpreserved samples and there are too many variables that influence measured concentrations. The target anions include chlorite, chlorate, bromate, and bromide by conductivity detection and bromate anions by postcolumn UV/VIS absorbance detection. The ion chromatographic system must utilize suppressed conductivity detection. The postcolumn reagent must be delivered pneumatically and some form of software signal filtering or smoothing of the absorbance signal must be incorporated. |
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Scope and Application
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This method determines oxyhalide disinfection by-product anions in reagent water, surface water, ground water, and finished drinking water. In addition, bromide can be accurately determined in source or raw water. |
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Applicable Concentration Range
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5 - 100 ug/L (conductivity detector); 0.5-15 ug/L (bromate; post-column reactor) |
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Interferences
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(A) Coelution: Direct chromatographic coelution, concentration dependent coelution, and ionic displacement effects (which can shift rentention times) can all cause interferences by coelution. It may be possible to overcome by adjusting chromatographic conditions (e.g., changing columns), diluting the sample, or using pretreatment cartridges. Care must be taken when using these steps to ensure that analyses are not adversely affected. (B) Contamination: Interferences may be caused by contaminants in the reagent water, reagents, glassware, and other sample processing apparatus that lead to discrete artifacts or elevated baselines. (C) Particulate: Samples containing particles > 0.45 um, and reagents containing particles > 0.20 um can damage chromatography columns and flow systems. Filtration should be use to prevent damage. (D) Carry over: Carry over peaks from one analysis to another may also cause interferences as false positives. (E) Chlorine dioxide: Sample matrices with residual chlorine dioxide will result in the formation of additional chlorite prior to analysis. (F) Chlorite: The presence of chlorite can interfere with the quantitation of low concentrations of bromate on the postcolunn UV/VIS absorbance detector. |
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Quality Control Requirements
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Initial Demonstration of Capability must show acceptable Demonstration of Accuracy (IDA) and Precision (IDP) and the Method Detection Limit (MDL) must be determined. Recovery for Laboratory Fortified Blanks (LFB) must be 75 - 125% from the Minimum Reporting Level (MRL) to 5X MRL. Recovery should be 75 - 125% for Laboratory Fortified Sample Matrix (LFM). Dichloroacetate is added as a surrogate and surrogate recovery must be 90 - 115%. Relative Percent Difference (RPD) for field or laboratory duplicates must be + or - 20% for concentrations ranging between the MRL to 5X the MRL. Peak Gaussian Factor (PGF) must fall between 0.80 and 1.15 Retention Time (RT) and the surrogate RT must remain 80% of the initial RT when the column was new. |
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Sample Handling
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Samples should be collected in pre-cleaned opaque plastic or amber glass bottles. If chlorine dioxide is present in the water then the samples must be sparged with helium or nitrogen prior to addition of ethylenediamine (EDA) preservative at the time of sample collection. EDA is added to make a concentration of 50 mg/L in the sample. Samples must be chilled and stored at <6 deg C. and must not exceed 10 deg C. during the first 48 hours after collection and their temperature must be confirmed to be below 10 deg. C. when received at the laboratory. |
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Maximum Holding Time
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14 days for chlorite; 28 days for chlorate, bromide and bromate |
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Relative Cost
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$51 to $200 |
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Sample Preparation Methods
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None |
