EPA-OGWDW/TSC: 515.3: Chlorinated Acids by GC/ECD
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Official Method Name
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Determination of Chlorinated Acids in Drinking Water by Liquid-Liquid Extraction, Derivitization, and Gas Chromatography with Electron Capture Detection |
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Current Revision
| Revision 1.0, July 1996 |
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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 alkaline pH for one hour to hydrolyze derivatives. The sample is then acidified and reagents are added to color the aqueous phase and to increase the ionic strength of the aqueous phase (which helps drive organic acids into an organic phase). The sample is then extracted with MTBE. The chlorinated acids in the MTBE organic phase are converted to their methyl esters using diazomethane or a base-promoted esterfication using TMA hydroxide followed by methyl iodide. The concentrations of esters (converted chlorinated acids) are measured using a capillary column gas chromatography (GC) equipped with an electron capture detector (ECD). Note: Method 515.3 does not have a solvent wash step prior to acidification and derivatization. Dacthal, the parent di-ester, as well as the mono- and di-acid metabolites would all be measured together. |
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Scope and Application
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This method determines certain chlorinated acids in drinking water, groundwater, raw source water, and water at any intermediate treatment stage. |
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Applicable Concentration Range
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Ranges differ for each analyte depending on matrix and interferences. |
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Interferences
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(A) Glassware contamination: Thoroughly clean glassware, including baking or solvent rinse. (B) Solvent contamination: Use high purity solvents, and test solvents to prevent contamination. (C) Contamination from sample carryover: Rinsing apparatus with MTBE between analyses can minimize contamination. (D) Extracted interferences: Interference from extracted non-target compounds, with retention times similar to target compounds, can be reduced by using confirmation analysis. (E) Phthalate ester interference: Avoid the use of plastics and use pure reagents to avoid contamination by these ubiquitous compounds. (F) Water: Water, from glassware or reagents, can cause incomplete methylation. (G) Chlorine: 5-Hydroxydicamba may not be recovered from chlorinated waters. |
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Quality Control Requirements
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Monitoring the laboratory performance check standard, initial demonstration of laboratory capability, performance of the method detection limit study, analysis of laboratory reagent blanks (LRBs), and laboratory fortified sample matrices, determination of surrogate compound recoveries in each sample and blank, monitoring internal standard peak area or height in each sample, blank, and CCC, and analysis of QC samples. Additional QC practices may be added. |
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Sample Handling
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Grab samples must be collected following conventional sampling practices using amber glass containers with TFE-lined screw caps. Dechlorinate samples using 4 mg of sodium thiosulfate per 50 mL of sample prior to collection. Overfill all bottles, making sure to leave no bubbles or headspace. After sample is collected, seal the bottle and swirl until the sodium thiosulfate is dissolved. Store samples at 4oC until analysis. |
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Maximum Holding Time
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All analytes are stable in water for 14 days, though stability should be checked. Extracts can be stored for 14 days. |
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Relative Cost
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$201 to $400 |
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Sample Preparation Methods
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