USGS-NWQL: O-5129-95: Organochlorine Pesticides and Gross Polychlorinated Biphenyls in Bottom Sediment by Gas Chromatography
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Official Method Name
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Determination of Ogranochlorine Pesticides and Polychlorinated Biphenyls in Bottom Sediment by Dual Capillary-Column Gas Chromatography with Electron-Capture Detection |
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Current Revision
| 1995 |
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Media
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SOILS/SEDIMENT |
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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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Foreman, W.T., Connor, B.F., Furlong, E.T., Vaught, D.G., and Merten, L.M., 1995, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory--Determination of organochlorine pesticides and polychlorinated biphenyls in bottom sediment by dual capillary-column gas chromatography with electron-capture detection: U.S. Geological Survey Open-File Report 94-351. |
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Brief Method Summary
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A 25-g equivalent dry-weight sample is Soxhlet extracted using dichloromethane, reduced in volume, and filtered. Two aliquots of the sample extract are quantitatively injected onto a styrene-divinylbenzene gel permeation column and eluted with dichloromethane. This gel permeation chromatography step removes inorganic sulfur and large natural molecules from the sediment extract. The first aliquot is analyzed for semivolatile organic compounds by gas chromatography with mass spectrometric detection. The second aliquot is further split into two fractions by combined alumina/silica adsorption chromatography prior to determination of the organochlorine pesticides and PCBs by dual capillary-column gas chromatography with electron-capture detection. |
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Scope and Application
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This method is suitable for the determination of 30 individual organochlorine pesticides, as well as total toxaphene, a complex OC pesticide mixture, and total PCBs in soil and sediment samples, with current (February 1995) reporting limits of 1 to 5 ug/kg of each individual pesticide, 50 ug/kg of total PCBs, and 200 ug/kg of total toxaphene. This method is applicable to samples of organochlorine pesticides and PCBs that are (1) efficiently extracted from the solid matrix by methanol or dichloromethane, (2) adequately separated from natural co-extracted compounds by gel permeation chromatography, (3) efficiently recovered from the alumina-over-silica adsorption chromatography fractionation step, and (4) sufficiently volatile and thermally stable for gas chromatographic analysis. |
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Applicable Concentration Range
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1-5 organochlorine pesticides; 50 total PCB: 200 toxaphene |
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Interferences
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Nonmethod organohalogen compounds and other ECD-sensitive compounds that are co-extracted, collected in the GPC fraction, and isolated in the two fractions produced in the alumina/silica adsorption chromatography step are potential interferents. The GC with dual-column confirmation helps minimize chromatographic interferences. For some samples, reliable detection might not be possible because of interferent levels, and reporting limits will have to be raised. Follow-up GC/MS analysis also may be used to verify compound identities if the GC/ECD response is sufficient to suggest adequate detection by GC/MS operated in the electron-impact or electron-capture negative ionization modes. Inorganic sulfur that is incompletely removed during the GPC step can interfere with the analysis of select fraction 1 (F1) compounds, especially some PCB components. High concentrations of a complex mixture might interfere with the determination of individual pesticides or other complex mixtures. For example, high PCB concentrations in F1 might interfere with p,p'-DDE determination. Similarly, high concentrations of toxaphene or technical chlordane components in fraction 2 (F2) will interfere with the determination of other individual F2 pesticides or another F2 complex pesticide mixture (for example, high technical chlordane component concentrations interfering with toxaphene determination). The presence of polychlorinated naphthalenes also might interfere with the determination of PCBs. |
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Quality Control Requirements
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Quality-control samples area analyzed at a minimum of one in every ten samples. These QC samples include at least one of each of the following: blanks, quality control samples, third party check solutions, replicates, and spikes. Correlation coefficients for calibration curves must be at least 0.995. Surrogate and spike results must fall within 3 standard deviations of the mean value. Calibration verification samples (TPC, CCV?s) must be within +/- 30 percent. If all of the data-acceptance criteria in the SOPs are met, then the analytical data are acceptable. |
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Sample Handling
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Place collected samples into 1,000-mL wide-mouth glass jars with PTFE-lined lids or other approved containers and store on ice until shipment. Ship samples on ice via overnight carrier to laboratory as soon as possible following collection. Upon receipt at the laboratory, carefully decant excess water above the sediment layer and store the samples at -15oC until analysis. |
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Maximum Holding Time
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Relative Cost
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Greater than $400 |
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Sample Preparation Methods
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