EPA Method 1664: Extracting Oil and Grease 12 Jul 2010: This application note presents a step-by-step guide to using Empore Oil and Grease Solid Phase Extraction Disks to replace the liquid-liquid n-hexane extraction technique for EPA Method 1664. A one litre water sample is passed through the disk and eluted with n-hexane. After drying, the residue is weighed and reported in mg/L as HEM. 3M Bioanalytical