Determination of Dissolved Oil and Grease

The dissolved oil and grease content is first determined by measuring the total oil and grease content and then subtracting the measured dispersed oil and grease content. The measured dispersed oil is obtained by removal of the dissolved oil and grease from the solvent with silica gel. This can be expressed by the following equation  

Dissolved organic matter is generally either polar or of low molecular weight. To remove the dissolved organic matter, the solvent extract is contacted (either in an adsorption column or by intimate mixing) with activated silica gel (e.g., Florisil) or alumina. The materials not adsorbed by the silica gel are described as dispersed oil and grease. 

In the absence of silica gel, filtration can be used to remove the dispersed oil and grease. In this technique the filtrate, obtained after passing through a 0.45-pm filter paper is left behind on the filter paper. The U.S. EPA uses the term petroleum hydrocarbons for dispersed oil and grease. 

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