Acrylamide is a monomer used in a variety of synthetic processes to form polymers and copolymers. It polymerizes in the presence of free radicals in aqueous solutions. It is usually used to prepare polyacrylamide gels for electrophoresis separation of biomolecules. Common reaction initiators are riboflavin and ammonium persulfate; varying the ratio of acrylamide to crosslinking agent permits the formation of a gel with predictable average pore size and texture. Acrylamide tends to hydrolyze under acidic or basic conditions to form acrylic acid. Polyacrylamide plastics have numerous commercial applications, due in part to the tendency of polyacrylamide to adsorb many times its own mass in water. Acrylic acid and any ionic impurities in the acrylamide can have significant effects on the performance of the acrylamide gel formed, since the voltage across the gel is affected by the ionic charge of the gel and usage buffers.