EPA-RCA: 9071B: Oil and grease in soils, sediments, sludges, and other solids by Soxhlet extraction
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Official Method Name
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n-Hexane Extractable Material (HEM) for Sludge, Sediment, and Solid Samples |
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Current Revision
| revision 2, April 1998 |
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Media
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SOILS/SEDIMENT |
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Instrumentation
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Analytical balance |
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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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A representative portion of wet (as received) waste is acidified with concentrated HCl and chemically dried with magnesium sulfate or sodium sulfate. Magnesium sulfate monohydrate is used to dry acidified sludges as it will combine with 75% of its own weight in water in forming magnesium sulfate heptahydrate. Anhydrous sodium sulfate is used to dry soil and sediment samples. After drying, the HEM is extracted with n-hexane using a Soxhlet apparatus. The n-hexane extract is then distilled from the extract and the HEM is desiccated and weighed. When necessary, a separate sample portion is evaluated for percent solids, and the dry weight fraction may be used to calculate the dry-weight HEM concentration of the soil, sediment, or waste. |
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Scope and Application
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Method 9071 is suitable for extracting relatively non-volatile hydrocarbons, vegetable oils, animal fats, waxes, soaps, greases, biological lipids, and related materials. Method 9071 is not recommended for measuring materials that volatilize at temperatures below 85 deg C. Petroleum fuels from gasoline through #2 fuel oil may be partially lost during the solvent removal process. |
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Applicable Concentration Range
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Not specified. |
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Interferences
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(A) Poor precision: Strict adherence to all details including consistent rate of cycling and time of extraction in the Soxhlet apparatus, consistent order and length of time required for drying and cooling extracted materials. (B) Contamination from solvents, reagents, glassware, and other sample-processing hardware: Process a method blank with each analytical batch. Specific selection of reagents, solvent washes, or purification of solvents may be required. Avoid use of plastic measuring devices, and/or plastic tubing attachments. Clean glassware by washing with hot tap water with detergent, rinsing with tap water and reagent water, and rinsing with solvent. Glassware may also be baked at 200-250 deg C for 1 hour. Boiling flasks that are used to contain the extracted residues may be dried in an oven at 105-115 deg C and stored in a desiccator until used. (C) Gradual increase in weight due to the absorption of oxygen or gradual loss of weight may result due to volatilization: Extracted residues should be maintained in a desiccator during cooling and prior to weighing. Extracted residues should be weighed as soon as possible after cooling. (D) Positive bias due to non-oily extractable substances such as sulfur compounds, organic dyes, and chlorophyll: For the purpose of this method, all materials extracted and retained during this procedure are defined as HEM. |
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Quality Control Requirements
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Method blanks, matrix duplicates, matrix spikes, Laboratory control samples (LCS). |
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Sample Handling
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A minimum of 100 grams of sample should be collected using a metal spatula, spoon, or equivalent device. Samples should be collected into a pre-cleaned wide-mouth glass container fitted with a TFE-lined screw cap. When practical (i.e., when the sample matrix allows the complete mixing of sample and acid such as with a pourable sludge or sediment), the sample should be preserved to a pH < 2 by adding 1 mL of concentrated HCl per 100 gram of sample and cooled to 4 ± 2 deg C. If acidification is not practical (as with a dry soil), the addition of the HCl is not required and the sample should be cooled to 4 ± 2 deg C. The laboratory must be notified ahead of time to acid the samples. |
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Maximum Holding Time
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A holding time has not been established for HEM in solids, but it is recommended that the sample be analyzed as soon as possible. |
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Relative Cost
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Unknown |
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Sample Preparation Methods
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See method for preparation of sludge/waste samples and soil/sediment samples. |
