EPA-EAD: 1664: Oil and Grease and Non-polar Material Using Solvent Extraction and Gravimetry
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Official Method Name
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N-Hexane Extractable Material (HEM; Oil and Grease) and Silica Gel Treated N-Hexane Extractable Material (SGT-HEM; Non-Polar Material) by Extraction and Gravimetry |
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Current Revision
| Revision A, February 1999 |
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Media
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WATER |
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Instrumentation
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Gravimetry |
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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 1-L sample is acidified and serially extracted three times with n-hexane in a separatory funnel. The extract is dried over sodium sulfate. The solvent is distilled from the extract and the residue from the extract is desiccated. The amount of HEM in the extract is measured by weighing the dry residue on a balance. If the HEM is to be used for determination of SGT-HEM, the HEM is redissolved in n-hexane and silica gel is added to remove polar materials. The solution is filtered to remove the silica gel, the solvent is distilled, and the residue is desiccated. The amount of SGT-HEM in the extract is measured by weighing the dry residue on a balance. |
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Scope and Application
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This method determines n-hexane extractable material (HEM; oil and grease) and n-hexane extractable material that is not adsorbed by silica gel (SGT-HEM; non-polar material) in surface and saline waters and industrial and domestic aqueous wastes. HEM includes relatively non-volatile hydrocarbons, vegetable oils, animal fats, waxes, soaps, greases, and related materials. |
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Applicable Concentration Range
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5 - 1000 mg/L |
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Interferences
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(A) Reagent contamination: Use high purity reagents. (B) Glassware contamination: Thoroughly clean glassware, including detergent wash and solvent rinse. (C) Interfering mass: Use a 0.45 micron filter if filter paper appears to allow the passage of sodium sulfate or silica gel fines that will be included in HEM/SGT-HEM weighing. (D) Emulsions: Use procedures in the method to break emulsions caused by complex matrices. |
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Quality Control Requirements
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The minimum recommended quality control requirements of this program consist of an initial demonstration of laboratory capability [analysis of initial precision and recovery samples (IPR), and determination of a method detection limit (MDL)], ongoing analysis of standards and blanks as a test of method performance. |
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Sample Handling
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Do not prerinse bottle with sample before collection. If analysis is to be delayed for more than four hours, adjust the sample pH to less than 2 with HCl or H2SO4 solution at the time of collection, and refrigerate at 0 to 4oC until the time of extraction. The high probability that extractable matter may adhere to sampling equipment and result in measurements that are biased low precludes the collection of composite samples. Therefore, samples must be collected as grab samples. If a composite measurement is required, individual grab samples collected at prescribed time intervals must be analyzed separately and the concentrations averaged. Alternatively, samples can be collected in the field and composited in the laboratory. |
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Maximum Holding Time
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28 days. |
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Relative Cost
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$51 to $200 |
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Sample Preparation Methods
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