The support medium provides the matrix in which separation takes place. Various types of support media are used in electrophoresis including gels and membranes. The sample for electrophorectic separation is placed on the gel or membrane. Common gels are cellulose acetate (formed by a chemical reaction of cellulose with acetic anhydride), agarose, and polyacrylamide. Cellulose requires soaking before sample application and a clearing step for detection of separated solutes or bands. Agarose gel is therefore used more often than cellulose acetate gel for clinical electrophoresis because it does not require these steps.
These gels are formed into sheets or slabs, or inserted into columns or tubes. The gel can be positioned horizontally or vertically.