EPA Method 548.1

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EPA Method 548.1:
Determination of Endothall in Drinking Water by Ion Exchange Extraction, c Acidic Methanol Methylation and Gas Chromatography/Mass Spectrometry -Revision 1.0.

A 100-mL sample is passed through a liquid/solid extraction (LSE) cartridge containing an intermediate strength, primarily tertiary amine anion exchanger mounted on a vacuum manifold and conditioned with appropriate solvents. Extracted endothall is eluted from the LSE cartridge with 8-mL of acidic methanol. After adding a small volume of methylene chloride as a co-solvent, the dimethyl ester of endothall is formed within 30 minutes with modest heating. After addition of salted reagent water, the ester is partitioned into 8-10 mL of methylene chloride. The extract volume is reduced with a nitrogen purge. The concentration of endothall in the extract is measured using a megabore capillary column gas chromatography (GC) system equipped with a mass spectrometer detector (MS) or a flame ionization detector (FID). A FID may be utilized for the determination of endothall, but must be supported by an additional analysis using a confirmatory gas chromatographic column.

This method determines endothall in drinking water sources and finished drinking water.

Methods for the Determination of Organic Compounds in Drinking Water - Supplement II (EPA/600/R-92-129)

(A) Glassware contamination: Thoroughly clean glassware, including baking or solvent rinse.(B) Reagent contamination: Use high purity reagents.(C) Ion interferences: Ca+2 and Mg+2 and sulfate lower recovery by interfering with the ion exchange process.(D) Extracted interferences: Interference from extracted non-target compounds, with retention times similar to target compounds, can be reduced by cleaning the extract.

QC Requirements:
Initial demonstration of laboratory capability, followed by analysis of laboratory reagent blanks (LRBs), laboratory fortified matrix samples, laboratory fortified blanks (LFBs), and QC check standards. A MDL also must be determined.

Maximum Holding Time:
7 days; 14 days for extracts.



Not specified in method. Range differs depending on matrix and instrumentation.


The MDL was determined using the standard deviation of 7 replicate analyses of an analyte-fortified reagent water sample (2 ug/L of endothall) 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, August 1992

Test Description:
Endothall by LSE & G

Report Number:

Instrument used for this test: