EPA-OGWDW/TSC: 552.3rev1.0: Haloacetic Acids and Dalapon in Drinking Water by Microextraction, Derivitization, and GC-ECD
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Official Method Name
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Determination of Haloacetic Acids and Dalapon in Drinking Water by Liquid-Liquid Microextraction, Derivitization, and Gas Chromatography With Electron Capture Detection |
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Current Revision
| Revision 1.0, July 2003 |
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Media
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WATER |
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Instrumentation
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Gas Chromatography with Electron Capture Detection |
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Method Subcategory
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Organic |
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Method Source
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Citation
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Brief Method Summary
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A 40 mL sample is adjusted to pH of 0.5 or less and extracted with 4 mL of either methyl tert-butyl ether (MTBE) or tert-amyl methyl ether (TAME) containing an internal standard (1,2,3-trichloropropane is recommended). Haloacetic acids that have been partitioned into the organic phase are converted to their methyl esters by addition of acidic methanol followed by heating for 2 hours. The solvent phase containing the methylated haloacetic acids is then separated from the acidic methanol by adding a concentrated aqueous solution of sodium sulfate. The extract is then neutralized with saturated solution of sodium bicarbonate and an aliquot of the solvent layer is analyzed by GC/ECD. |
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Scope and Application
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This method determines haloacetic acids and dalapon in drinking water by GC-ECD. |
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Applicable Concentration Range
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0.5 - 30 ug/L |
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Interferences
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(A) Contamination (general): Interferences may be caused by contaminants in solvents, reagents (including sodium sulfate), glassware, and other sample processing apparatus that lead to discrete artifacts or elevated baselines. The ester of bromochloroacetic acid coelutes with a low-level interferent on both the primary and confirmation GC columns (it may be dimethyl sulfide from the sodium sulfate). Some lots of TAME contain interferants including one that coelutes with the ester of monochloroacetic acid. To minimize potential interferences, glassware must be thoroughly cleaned and blanks should be analyzed to test for contamination. (B) Matrix interferences: Matrix interferences may be caused by contaminants that are extracted from the sample and will vary from source to source. (C) Phthalate esters: Phthalate esters can pose serious interferences with the electron capture detector (ECD) so plastics should be avoided in the laboratory. In addition, exhaustive purification of glassware and reagents may be required. |
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Quality Control Requirements
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Initial demonstration of accuracy (which must be + or - 30% of fortified value), precision (RSD must be <20%) and low system background are required. Calibration and continuing calibration checks (CCC) are required plus an internal standard and the detection level must be determined over a 3 day period. A field duplicate (FD) and a Laboratory Fortified Sample Matrix (LFSM) and laboratory reagent blanks (LRB) are required with each analysis batch. Quality Control Samples (QCS) must be analyzed when new primary dilution standards are prepared (or quarterly) and the internal standard calibration technique must be used for calibration curves. Subtracting blank values from sample results is not permitted. |
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Sample Handling
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Collect grab samples using amber glass containers with PTFE-lined screw caps and at least 50 mL capacity. Prior to shipment crystalline or granular ammonium chloride is added to sample containers to produce a concentration of 100 mg/L in the sample to convert free chlorine residual to combined chlorine. Headspace free samples are not necessary. Remove any aerators from the tap and flush the system until the water temperature stabilizes. Samples must be chilled during shipment and must not exceed 10 deg. C. during the first 48 hours after collection. Samples must be held at or below 6 deg. C (but not frozen) and protected from light until extraction. |
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Maximum Holding Time
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14 days (sample); 21 days (MTBE extract); 28 days (TAME extract) |
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Relative Cost
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$51 to $200 |
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Sample Preparation Methods
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