EPA Method 515.3

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EPA Method 515.3:
Chlorinated Acids by GC/ECD. Official Name: Determination of Chlorinated Acids in Drinking Water by Liquid-Liquid Extraction, Derivitization, and Gas Chromatography with Electron Capture Detection

Summary:
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.

Scope:
This method determines certain chlorinated acids in drinking water, groundwater, raw source water, and water at any intermediate treatment stage.

Citation:
Methods for the Determination of Organic and Inorganic Compounds in Drinking Water, Volume 1 (EPA/815-R-00-014)

Interferences:
(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.

QC Requirements:
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.

Maximum Holding Time:
All analytes are stable in water for 14 days, though stability should be checked.Extracts can be stored for 14 days.

Media:
WATER

Subcategory:
Organic

Concentration:
Ranges differ for each analyte depending on matrix and interferences.

Precision:
Precision and accuracy values were calculated using seven replicate analyses of fortified reagent water samples. Additional data are available in the method.

Detection:
MDLs were determined using the standard deviation of 7 replicate analyses of an analyte-fortified reagent water sample multiplied by the t-value for 6 degrees of freedom at the 99% confidence level. Detailed instructions for how MDLs are determined are found at 40 CFR part 136, Appendix B.

Revision Number:
Revision 1.0, July 1996