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View Actual EPA Method 508 (PDF File)
EPA Method 508:Determination of Chlorinated Pesticides in Water by Gas Chromatography with an Electron Capture Detector - Revision 3.1.
Summary:A 1-L sample is extracted with methylene chloride by shaking in a separatory funnel or mechanical tumbling in a bottle. The methylene chloride extract is isolated, dried and concentrated after solvent substitution with methyl tert-butyl ether (MTBE). The concentrations of pesticides in the extract are measured using a capillary column gas chromatography (GC) system equipped with an electron capture detector (ECD).NOTE: CAS Numbers in NEMI for cis- and trans- permethrin differ from those in the method. The CAS Numbers in NEMI are the correct ones.
Scope:This method determines certain chlorinated pesticides in groundwater and finished drinking water.
Citation:Methods for the Determination of Organic Compounds in Drinking Water - Supplement III (EPA/600/R-95-131)
Interferences:(A) Glassware contamination: Thoroughly clean glassware, including baking or solvent rinse.(B) Reagent contamination: Use high purity reagents.(C) Phthalate ester interference: Avoid the use of plastics and use pure reagents to avoid contamination by these ubiquitous compounds.(D) Contamination from sample carryover: Rinsing apparatus with MTBE between analyses can minimize contamination.(E) Extracted interferences: Interference from extracted non-target compounds, with retention times similar to target compounds, can be reduced by using confirmation analysis.(F) Variable solvents: Use the same solvent for each analysis.
QC Requirements:Initial demonstration of laboratory capability, determination of surrogate compound recoveries in each sample and blank, monitoring internal standard peak area or height in each sample and blank (when internal standard calibration procedures are being employed), analysis of laboratory reagent blanks (LRBs), laboratory fortified samples, laboratory fortified blanks (LFBs), and QC samples. A MDL for each analyte must also be determined.
Maximum Holding Time:7 days generally (see Sample Handling for exceptions). Extracts within 14 days.
Media:WATER
Subcategory:Organic
Concentration:Ranges differ for each analyte.
Precision:Method precision and accuracy values were generated using 7 to 8 replicate analyses of fortified reagent water. The method contains additional data characterizing method performance. NOTES: (1) PCBs and chlordane are regulatory parameters representing the sum of specific compounds. See performance data for speicifc Arolclors and chlordanes, respectively. (2) This method is approved (as of 2002) for analysis of cyclohexapentadiene, though the analyte is not listed in the method. Check regulatory information for current status. NOTE: CAS Numbers in NEMI for cis- and trans- permethrin differ from those in the method. The CAS Numbers in NEMI are the correct ones.
Detection:MDLs were determined using the standard deviation of 7 to 8 replicate analyses of an analyte-fortified reagent water sample multiplied by the t-value for (# of samples - 1) 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 3.1, 1995