Method 1664A

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)


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Method Data

Hold Times, Preservatives, Preps, Collection, Analytical & Documentation
Holding Time:   28 days from sample collection to analysis.
Preservatives:   Refrigerate samples at at 0-4°C from the time of collection until extraction.
Required Preps:   1-L glass bottle with PTFE-lined screw cap
Collection Method:   Grab sampling
Analytical Methodology:   Extraction and Gravimetry
Documentation:   1664A

Analyte List*

Analyte Formula CAS Number Detection Limit
Oil & Grease
Total Petroleum Hydrocarbons

* The analytes and detection limits listed for each method represent the typical detection limits and analytes reported for that particular method. Keep in mind that analyte lists may vary from laboratory to laboratory. Detection limits may also vary from lab to lab and are dependent upon the sample size, matrix, and any interferences that may be present in the sample.