EPA-OGWDW/TSC: 527: Pesticides and flame retardants in water by SPE and capillary column GC/MS
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Official Method Name
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Determination of selected pesticides and flame retardants in drinking water by solid phase extraction and capillary column gas chromatography/mass spectrometry (GC/MS) |
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Current Revision
| Rev. 1.0, April 2005 |
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Media
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WATER |
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Instrumentation
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Gas Chromatography with Mass Spectrometry 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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Price, E.K., Prakash, B., Domino, M.M., Pepich, B.V., and Munch, D.J., 2005, Determination of selected pesticides and flame retardants in drinking water by solid phase extraction and capillary column gas chromatography/mass spectrometry: U.S. Environmental Protection Agency Report EPA/815/R-05/005, Version 1.0, 44 p. |
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Brief Method Summary
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A 1-liter water sample is fortified with surrogates and passed through a solid phase extraction disk containing polystyrene-divinyl-benzene to extract the target analytes and surrogates. The compounds are eluted from the solid phase with a small amount of ethyl acetate and methylene chloride. The extract is dried by passing it through a column of anhydrous sodium sulfate, concentrated with nitrogen, and then adjusted to a 1-mL volume with ethyl acetate after adding the internal standard. A 1-uL, split-less injection is made into a GC equipped with a high-resolution fused silica capillary column that is interfaced to a MS. The analytes are separated and identified by comparing the acquired mass spectra and retention times to reference spectra and retention times for calibration standards acquired under identical GC/MS conditions. The concentration of each analyte is determined by using the internal standard technique. Surrogate analytes are added to all Field and Quality Control Samples to monitor the extraction efficiency of the target analytes. |
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Scope and Application
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This method is for the determination of selected semivolatile organic compounds in drinking water. |
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Applicable Concentration Range
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Concentration range is dependent on the instrument calibration range. |
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Interferences
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Glassware must be cleaned by washing with detergent and tap water, and rinsing with tap and reagent water. Method interferences may be caused by contaminants in solvents, reagents, sample bottles and caps, and other sample processing hardware that lead to discrete artifacts and/or elevated baselines in the chromatograms. These must be routinely demonstrated to be free from interferences under the conditions of the analysis by analyzing laboratory reagent blanks. Subtracting blank values from sample results is not permitted. Matrix interferences may be caused by contaminants that are co-extracted from the sample. The extent these interferences will vary from source to source, depending upon the nature of the water. The potential exists for trace-level organic contaminants in the relatively large quantities of buffer and preservatives added to sample bottles. Interferences from these sources should be monitored by analysis of laboratory reagent blanks. Solid phase extraction disks have been observed to be a source of interferences and the analysis of field and laboratory reagent blanks can verify the presence or absence of such interferences. Analyte carryover may occur when a relatively clean sample is analyzed immediately after a sample containing relatively high concentrations of compounds. Repeated injections of the same autosampler vial, may cause silicone compounds to be leached from a punctured autosampler vial septa. These appear as regularly spaced chromatographic peaks with similar fragmentation patterns and can unnecessarily complicate the total ion chromatograms, causing interferences at high levels. Bromacil should be reviewed for potential common interferences. The quantitation ion suggested (205 m/z) can be found in the SDVB solid phase. Method blanks should be carefully examined for this potential interference. The ion at 207 m/z may be used as an alternate quantitation ion; however, this ion is associated with column bleed. |
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Quality Control Requirements
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Each laboratory using this method is required to operate a formal quality control program. At a minimum, this program should consist of an initial demonstration of laboratory capability; measurement of the surrogate compound in each sample; and analysis of laboratory reagent blanks, laboratory fortified blanks, laboratory fortified matrix samples, and quality control check standards. |
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Sample Handling
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Grab samples are collected using a 1-L or 1-quart amber bottle fitted with a PTFE-lined screw-cap. Preservation reagents are added to each sample bottle prior to shipment. Residual chlorine must be reduced at the time of sample collection with 100 mg of ascorbic acid per liter. Trisodium EDTA must be added to inhibit metal-catalyzed hydrolysis of the target analytes. The sample must be buffered to pH 3.8 using potassium dihydrogen citrate. Samples must be chilled during shipment and must not exceed 10oC during the first 48 hours after collection. Sample temperature must be confirmed to be at or below 10oC when they are received at the laboratory. Samples stored in the lab must be held at or below 6oC until extraction, but should not be frozen. Sample extracts must be stored at 0oC or less. |
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Maximum Holding Time
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Sample holding time is up to 14 days when properly collected, dechlorinated, preserved, shipped, and stored; sample extracts must be analyzed within 28 days after extraction. |
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Relative Cost
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$201 to $400 |
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Sample Preparation Methods
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