The Oil & Grease Disk was specifically designed for EPA Method 1664 (N-Hexane Extractable Materials (HEM) and Silica Gel Treated N-Hexane Extractable Material (SGT-HEM) by Extraction and Gravimetry). EPA Method 1664 Revision A was approved for use in the United States and published in the Federal Register on May 14, 1999. The Oil & Grease Disk incorporates C18 sorbent particles within a hydrophobic matrix. For EPA Method 1664, C18 extractable materials are collected from waste water. These materials are eluted from the disk using hexane.