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
By EPA 1664
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.
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.
-EPA Methods and Guidance for Analysis of Water, Version 2.0
|Hold Time||28 days|
|Preservation||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.|
|Sample Volume||1 Liter|
|Method Refernce||EPA 1664|
|n-hexane extractable material (HEM; oil and grease)|
|n-hexane extractable material that is not adsorbed by silica gel (SGT-HEM; non-polar material)|
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