Standard Methods: 6630 C: Organochlorine Pesticides in Water by GC
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Official Method Name
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Organochlorine Pesticides in Water by Liquid-Liquid Extraction and Gas Chromatography |
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Current Revision
| Standard Methods Online |
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Media
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WATER |
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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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Brief Method Summary
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Pour measured sample into a separatory funnel. Extract with methylene chloride as in Method 6410-B, without pH adjustment or solvent wash. After concentrating with a 3-ball Snyder column, bring water bath to 80oC, remove the column, add 50 mL hexane, and reattach the column. Concentrate again, but use hexane to pre-wet the column. Cool, remove concentrator tube, and rinse joint with hexane. Stopper or seal the tube containing the sample. If sample cleanup is required, follow one of the following procedures: I. Magnesia-silica gel column cleanup - Pour 20 g magnesia-silica gel into a column and add 1 to 2 cm anhydrous granular Na2SO4 to the top. Pre-elute column with 60 mL hexane and discard eluate. Just before the sulfate layer is exposed to air, bring sample extract up to 10 mL with hexane and transfer the sample onto the column. Rinse the sample extract container twice with 1 to 2 mL hexane and add to the column. Make the following elutions in order, collecting eluates separately: 200 mL 6% ethyl ether in hexane; 200 mL 15% ethyl ether in hexane; and, 200 mL 50% ethyl ether in hexane. Concentrate samples as above, but use hexane to pre-wet the column and set the water bath to 85oC. Cool, remove concentrator tube, and rinse joint with hexane. Bring volume up to 10 mL and analyze sample. II. Sulfur interference removal - Add 1 to 3 drops of Hg to 1 mL concentrated extract in a concentrator tube or TFE-sealed vial, seal, and mix for 15 to 30 seconds. Operate the GC equipped with an electron capture detector so as to meet the retention times and MDLs as listed in Table 6630. III. Calibrate the GC system daily by either the external or internal standard procedure. This method is equivalent to EPA Method 608; see EMSLC 608. |
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Scope and Application
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This method is applicable to the determination of organochlorines in waste and wastewater. |
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Applicable Concentration Range
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4xMDL - 1000xMDL. Chlordane recovery at 4xMDL was low (60%). Toxaphene recovery is linear over range from 10xMDL-1000xMDL. [Note: (MDL) = Method Detection Limit] |
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Interferences
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(1) Contamination of samples, solvent, and carrier gases with target analytes (especially compounds common to environmental laboratories, like methylene chloride). (2) Contamination of samples with sulfur (primarily present in base-neutral fractions). (3) Septum bleed (compounds from the injection septum are analyzed with the sample). (4) Column bleed (compounds from column coating break down, decreasing column efficiency). (5) Ghost peaks (compounds adsorb strongly to the column and carry over to later runs). (6) Coelution of species. (7) Coextracted contaminants. (8) Phthalate esters interfere with detection of pesticides via electron capture detector. |
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Quality Control Requirements
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QCS, CB, MB |
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Sample Handling
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Collect duplicate samples in 1 L glass containers, with a TFE-lined screw cap. Refrigerate samples and extracts at 4oC until analysis. If samples are not to be extracted before 72 hours, adjust pH between 5 and 9 with NaOH or H2SO4. If determining aldrin and residual chlorine is present, add sodium thiosulfate. Extract samples within 7 days. Analyze extracts within 40 days. |
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Maximum Holding Time
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7 days (prior to extraction) 40 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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