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
This method is for determination of 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. A 1-L sample is acidified to pH <2 and serially extracted three times with n-hexane in a separatory funnel. The extract is dried over sodium sulfate, the solvent distilled from the extract and the HEM is desiccated and weighed. If the HEM is to be used for determination of SGT-HEM, the HEM is redissolved in n-hexane. For SGT-HEM determination, an amount of silica gel proportionate to the amount of HEM is added to the solution containing the redissolved HEM to remove polar materials. The solution is filtered to remove the silica gel, the solvent is distilled, and the SGT-HEM is desiccated and weighed.
Extractable materials that may be determined in addition to aqueous matrices are relatively non-volatile hydrocarbons, vegetable oils, animal fats, waxes, soaps, greases, and related materials. The method is based on prior Environmental Protection Agency (EPA) methods for determination of oil and grease and total petroleum hydrocarbons. The method detection limit (MDL) for HEM in Method 1664, Revision A is 1.4 mg/L and the minimum level of quantitation (ML) is 5.0 mg/L.
This method uses normal hexane (n-hexane) as the extraction solvent in place of 1,1,2-trichloro- 1,2,2-trifluoroethane (CFC-113; Freon-113), a Class 1 CFC (chlorofluorocarbon).
NOTE: This method replaces SW-846 Method 9070A.
(EPA: Office of Water)